• MySQL 5.1 Reference Manual :: 12 SQL Statement Syntax :: 12.1 Data Definition Statements :: 12.1.17 CREATE TABLE Syntax
  • 12.1.17. CREATE TABLE Syntax





        { LIKE old_tbl_name | (LIKE old_tbl_name) }
        col_name column_definition
      | [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...)
          [index_option] ...
      | {INDEX|KEY} [index_name] [index_type] (index_col_name,...)
          [index_option] ...
      | [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY]
          [index_name] [index_type] (index_col_name,...)
          [index_option] ...
      | {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name] (index_col_name,...)
          [index_option] ...
      | [CONSTRAINT [symbol]] FOREIGN KEY
          [index_name] (index_col_name,...) reference_definition
      | CHECK (expr)
        data_type [NOT NULL | NULL] [DEFAULT default_value]
          [COMMENT 'string']
      | TINYINT[(length)] [UNSIGNED] [ZEROFILL]
      | SMALLINT[(length)] [UNSIGNED] [ZEROFILL]
      | INT[(length)] [UNSIGNED] [ZEROFILL]
      | INTEGER[(length)] [UNSIGNED] [ZEROFILL]
      | BIGINT[(length)] [UNSIGNED] [ZEROFILL]
      | REAL[(length,decimals)] [UNSIGNED] [ZEROFILL]
      | DOUBLE[(length,decimals)] [UNSIGNED] [ZEROFILL]
      | FLOAT[(length,decimals)] [UNSIGNED] [ZEROFILL]
      | DECIMAL[(length[,decimals])] [UNSIGNED] [ZEROFILL]
      | NUMERIC[(length[,decimals])] [UNSIGNED] [ZEROFILL]
      | DATE
      | TIME
      | DATETIME
      | YEAR
      | CHAR[(length)]
          [CHARACTER SET charset_name] [COLLATE collation_name]
      | VARCHAR(length)
          [CHARACTER SET charset_name] [COLLATE collation_name]
      | BINARY[(length)]
      | VARBINARY(length)
      | TINYBLOB
      | BLOB
      | LONGBLOB
          [CHARACTER SET charset_name] [COLLATE collation_name]
      | TEXT [BINARY]
          [CHARACTER SET charset_name] [COLLATE collation_name]
          [CHARACTER SET charset_name] [COLLATE collation_name]
          [CHARACTER SET charset_name] [COLLATE collation_name]
      | ENUM(value1,value2,value3,...)
          [CHARACTER SET charset_name] [COLLATE collation_name]
      | SET(value1,value2,value3,...)
          [CHARACTER SET charset_name] [COLLATE collation_name]
      | spatial_type
        col_name [(length)] [ASC | DESC]
        KEY_BLOCK_SIZE [=] value
      | index_type
      | WITH PARSER parser_name
        REFERENCES tbl_name (index_col_name,...)
          [ON DELETE reference_option]
          [ON UPDATE reference_option]
        table_option [[,] table_option] ...
        ENGINE [=] engine_name
      | AUTO_INCREMENT [=] value
      | AVG_ROW_LENGTH [=] value
      | [DEFAULT] CHARACTER SET [=] charset_name
      | CHECKSUM [=] {0 | 1}
      | [DEFAULT] COLLATE [=] collation_name
      | COMMENT [=] 'string'
      | CONNECTION [=] 'connect_string'
      | DATA DIRECTORY [=] 'absolute path to directory'
      | DELAY_KEY_WRITE [=] {0 | 1}
      | INDEX DIRECTORY [=] 'absolute path to directory'
      | INSERT_METHOD [=] { NO | FIRST | LAST }
      | KEY_BLOCK_SIZE [=] value
      | MAX_ROWS [=] value
      | MIN_ROWS [=] value
      | PACK_KEYS [=] {0 | 1 | DEFAULT}
      | PASSWORD [=] 'string'
      | UNION [=] (tbl_name[,tbl_name]...)
            { [LINEAR] HASH(expr)
            | [LINEAR] KEY(column_list)
            | RANGE(expr)
            | LIST(expr) }
        [PARTITIONS num]
            { [LINEAR] HASH(expr)
            | [LINEAR] KEY(column_list) }
          [SUBPARTITIONS num]
        [(partition_definition [, partition_definition] ...)]
        PARTITION partition_name
            [VALUES {LESS THAN {(expr) | MAXVALUE} | IN (value_list)}]
            [[STORAGE] ENGINE [=] engine_name]
            [COMMENT [=] 'comment_text' ]
            [DATA DIRECTORY [=] 'data_dir']
            [INDEX DIRECTORY [=] 'index_dir']
            [MAX_ROWS [=] max_number_of_rows]
            [MIN_ROWS [=] min_number_of_rows]
            [TABLESPACE [=] tablespace_name]
            [NODEGROUP [=] node_group_id]
            [(subpartition_definition [, subpartition_definition] ...)]
        SUBPARTITION logical_name
            [[STORAGE] ENGINE [=] engine_name]
            [COMMENT [=] 'comment_text' ]
            [DATA DIRECTORY [=] 'data_dir']
            [INDEX DIRECTORY [=] 'index_dir']
            [MAX_ROWS [=] max_number_of_rows]
            [MIN_ROWS [=] min_number_of_rows]
            [TABLESPACE [=] tablespace_name]
            [NODEGROUP [=] node_group_id]
        [IGNORE | REPLACE] [AS] SELECT ...   (Some legal select statement)

    CREATE TABLE creates a table with the given name. You must have the CREATE privilege for the table.

    Rules for allowable table names are given in Section 8.2, “Schema Object Names”. By default, the table is created in the default database. An error occurs if the table exists, if there is no default database, or if the database does not exist.

    The table name can be specified as db_name.tbl_name to create the table in a specific database. This works regardless of whether there is a default database, assuming that the database exists. If you use quoted identifiers, quote the database and table names separately. For example, write `mydb`.`mytbl`, not `mydb.mytbl`.

    You can use the TEMPORARY keyword when creating a table. A TEMPORARY table is visible only to the current connection, and is dropped automatically when the connection is closed. This means that two different connections can use the same temporary table name without conflicting with each other or with an existing non-TEMPORARY table of the same name. (The existing table is hidden until the temporary table is dropped.) To create temporary tables, you must have the CREATE TEMPORARY TABLES privilege.


    CREATE TABLE does not automatically commit the current active transaction if you use the TEMPORARY keyword.

    The keywords IF NOT EXISTS prevent an error from occurring if the table exists. However, there is no verification that the existing table has a structure identical to that indicated by the CREATE TABLE statement.

    MySQL represents each table by an .frm table format (definition) file in the database directory. The storage engine for the table might create other files as well. In the case of MyISAM tables, the storage engine creates data and index files. Thus, for each MyISAM table tbl_name, there are three disk files.

    File Purpose
    tbl_name.frm Table format (definition) file
    tbl_name.MYD Data file
    tbl_name.MYI Index file

    Chapter 13, Storage Engines, describes what files each storage engine creates to represent tables. If a table name contains special characters, the names for the table files contain encoded versions of those characters as described in Section 8.2.3, “Mapping of Identifiers to File Names”.

    data_type represents the data type in a column definition. spatial_type represents a spatial data type. The data type syntax shown is representative only. For a full description of the syntax available for specifying column data types, as well as information about the properties of each type, see Chapter 10, Data Types, and Section 11.13, “Spatial Extensions”.

    Some attributes do not apply to all data types. AUTO_INCREMENT applies only to integer and floating-point types. DEFAULT does not apply to the BLOB or TEXT types.

    • If neither NULL nor NOT NULL is specified, the column is treated as though NULL had been specified.

    • An integer or floating-point column can have the additional attribute AUTO_INCREMENT. When you insert a value of NULL (recommended) or 0 into an indexed AUTO_INCREMENT column, the column is set to the next sequence value. Typically this is value+1, where value is the largest value for the column currently in the table. AUTO_INCREMENT sequences begin with 1.

      To retrieve an AUTO_INCREMENT value after inserting a row, use the LAST_INSERT_ID() SQL function or the mysql_insert_id() C API function. See Section 11.11.3, “Information Functions”, and Section, “mysql_insert_id().

      If the NO_AUTO_VALUE_ON_ZERO SQL mode is enabled, you can store 0 in AUTO_INCREMENT columns as 0 without generating a new sequence value. See Section 5.1.7, “Server SQL Modes”.


      There can be only one AUTO_INCREMENT column per table, it must be indexed, and it cannot have a DEFAULT value. An AUTO_INCREMENT column works properly only if it contains only positive values. Inserting a negative number is regarded as inserting a very large positive number. This is done to avoid precision problems when numbers “wrap” over from positive to negative and also to ensure that you do not accidentally get an AUTO_INCREMENT column that contains 0.

      For MyISAM tables, you can specify an AUTO_INCREMENT secondary column in a multiple-column key. See Section 3.6.9, “Using AUTO_INCREMENT.

      To make MySQL compatible with some ODBC applications, you can find the AUTO_INCREMENT value for the last inserted row with the following query:

      SELECT * FROM tbl_name WHERE auto_col IS NULL

      For information about InnoDB and AUTO_INCREMENT, see Section, “AUTO_INCREMENT Handling in InnoDB.

    • Character data types (CHAR, VARCHAR, TEXT) can include CHARACTER SET and COLLATE attributes to specify the character set and collation for the column. For details, see Section 9.1, “Character Set Support”. CHARSET is a synonym for CHARACTER SET. Example:

      CREATE TABLE t (c CHAR(20) CHARACTER SET utf8 COLLATE utf8_bin);

      MySQL 5.1 interprets length specifications in character column definitions in characters. (Versions before MySQL 4.1 interpreted them in bytes.) Lengths for BINARY and VARBINARY are in bytes.

    • The DEFAULT clause specifies a default value for a column. With one exception, the default value must be a constant; it cannot be a function or an expression. This means, for example, that you cannot set the default for a date column to be the value of a function such as NOW() or CURRENT_DATE. The exception is that you can specify CURRENT_TIMESTAMP as the default for a TIMESTAMP column. See Section, “TIMESTAMP Properties”.

      If a column definition includes no explicit DEFAULT value, MySQL determines the default value as described in Section 10.1.4, “Data Type Default Values”.

      BLOB and TEXT columns cannot be assigned a default value.

      CREATE TABLE fails if a date-valued default is not correct according to the NO_ZERO_IN_DATE SQL mode, even if strict SQL mode is not enabled. For example, c1 DATE DEFAULT '2010-00-00' causes CREATE TABLE to fail with Invalid default value for 'c1'.

      Native default value handling in MySQL Cluster NDB 7.0.15, MySQL Cluster NDB 7.1.4, and later.  Starting with MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB 7.1.4, default values for table columns are stored by NDBCLUSTER, rather than by the MySQL server as was previously the case. Because less data must be sent from an SQL node to the data nodes, inserts on tables having column value defaults can be performed more efficiently than before.

      Tables created using MySQL Cluster releases previous to the introduction of native default value support can still be used in MySQL Cluster NDB 7.0.15 and later, as well as well as MySQL Cluster NDB 7.1.4 and later. However, such tables continue to use defaults supplied by the MySQL server until they are upgraded. This upgrade can be done by means of an offline ALTER TABLE statement.


      You cannot set or change a table column's default value using an online ALTER TABLE operation

      Tables created in versions of MySQL Cluster that support native default values cannot be used with versions of MySQL Cluster that lack this support.

      NDBCLUSTER tables supporting native default values are still subject to the restrictions on default values imposed by the MySQL server. For more information, see Section 10.1.4, “Data Type Default Values”.

    • A comment for a column can be specified with the COMMENT option, up to 255 characters long. The comment is displayed by the SHOW CREATE TABLE and SHOW FULL COLUMNS statements.

    • Beginning with MySQL Cluster NDB 6.2.5 and MySQL Cluster NDB 6.3.2, it is also possible to specify a data storage format for individual columns of NDB tables using COLUMN_FORMAT. Allowable column formats are FIXED, DYNAMIC, and DEFAULT. FIXED is used to specify fixed-width storage, DYNAMIC allows the column to be variable-width, and DEFAULT causes the column to use fixed-width or variable-width storage as determined by the column's data type (possibly overridden by a ROW_FORMAT specifier).

      For NDB tables, the default value for COLUMN_FORMAT is DEFAULT.

      COLUMN_FORMAT currently has no effect on columns of tables using storage engines other than NDB.

    • For NDB tables, beginning with MySQL Cluster NDB 6.2.5 and MySQL Cluster NDB 6.3.2, it is also possible to specify whether the column is stored on disk or in memory by using a STORAGE clause. STORAGE DISK causes the column to be stored on disk, and STORAGE MEMORY causes in-memory storage to be used. The CREATE TABLE statement used must still include a TABLESPACE clause:

      mysql> CREATE TABLE t1 (
          ->     c1 INT STORAGE DISK,
          ->     c2 INT STORAGE MEMORY
          -> ) ENGINE NDB;
      ERROR 1005 (HY000): Can't create table 'c.t1' (errno: 140)
      mysql> CREATE TABLE t1 (
          ->     c1 INT STORAGE DISK,
          ->     c2 INT STORAGE MEMORY
          -> ) TABLESPACE ts_1 ENGINE NDB;
      Query OK, 0 rows affected (1.06 sec)

      For NDB tables, STORAGE DEFAULT is equivalent to STORAGE MEMORY.

      The STORAGE clause has no effect on tables using storage engines other than NDB.

    • KEY is normally a synonym for INDEX. The key attribute PRIMARY KEY can also be specified as just KEY when given in a column definition. This was implemented for compatibility with other database systems.

    • A UNIQUE index creates a constraint such that all values in the index must be distinct. An error occurs if you try to add a new row with a key value that matches an existing row. For all engines, a UNIQUE index allows multiple NULL values for columns that can contain NULL.

    • A PRIMARY KEY is a unique index where all key columns must be defined as NOT NULL. If they are not explicitly declared as NOT NULL, MySQL declares them so implicitly (and silently). A table can have only one PRIMARY KEY. If you do not have a PRIMARY KEY and an application asks for the PRIMARY KEY in your tables, MySQL returns the first UNIQUE index that has no NULL columns as the PRIMARY KEY.

      In InnoDB tables, having a long PRIMARY KEY wastes a lot of space. (See Section 13.6.10, “InnoDB Table and Index Structures”.)

    • In the created table, a PRIMARY KEY is placed first, followed by all UNIQUE indexes, and then the nonunique indexes. This helps the MySQL optimizer to prioritize which index to use and also more quickly to detect duplicated UNIQUE keys.

    • A PRIMARY KEY can be a multiple-column index. However, you cannot create a multiple-column index using the PRIMARY KEY key attribute in a column specification. Doing so only marks that single column as primary. You must use a separate PRIMARY KEY(index_col_name, ...) clause.

    • If a PRIMARY KEY or UNIQUE index consists of only one column that has an integer type, you can also refer to the column as _rowid in SELECT statements.

    • In MySQL, the name of a PRIMARY KEY is PRIMARY. For other indexes, if you do not assign a name, the index is assigned the same name as the first indexed column, with an optional suffix (_2, _3, ...) to make it unique. You can see index names for a table using SHOW INDEX FROM tbl_name. See Section, “SHOW INDEX Syntax”.

    • Some storage engines allow you to specify an index type when creating an index. The syntax for the index_type specifier is USING type_name.


      CREATE TABLE lookup
        (id INT, INDEX USING BTREE (id))
        ENGINE = MEMORY;

      Before MySQL 5.1.10, USING can be given only before the index column list. As of 5.1.10, the preferred position is after the column list. Use of the option before the column list will no longer be recognized in a future MySQL release.

      index_option values specify additional options for an index. USING is one such option. For details about allowable index_option values, see Section 12.1.13, “CREATE INDEX Syntax”.

      For more information about indexes, see Section 7.4.4, “How MySQL Uses Indexes”.

    • In MySQL 5.1, only the MyISAM, InnoDB, and MEMORY storage engines support indexes on columns that can have NULL values. In other cases, you must declare indexed columns as NOT NULL or an error results.

    • For CHAR, VARCHAR, BINARY, and VARBINARY columns, indexes can be created that use only the leading part of column values, using col_name(length) syntax to specify an index prefix length. BLOB and TEXT columns also can be indexed, but a prefix length must be given. Prefix lengths are given in characters for nonbinary string types and in bytes for binary string types. That is, index entries consist of the first length characters of each column value for CHAR, VARCHAR, and TEXT columns, and the first length bytes of each column value for BINARY, VARBINARY, and BLOB columns. Indexing only a prefix of column values like this can make the index file much smaller. See Section 7.4.2, “Column Indexes”.

      Only the MyISAM and InnoDB storage engines support indexing on BLOB and TEXT columns. For example:

      CREATE TABLE test (blob_col BLOB, INDEX(blob_col(10)));

      Prefixes can be up to 1000 bytes long (767 bytes for InnoDB tables). Note that prefix limits are measured in bytes, whereas the prefix length in CREATE TABLE statements is interpreted as number of characters for nonbinary data types (CHAR, VARCHAR, TEXT). Take this into account when specifying a prefix length for a column that uses a multi-byte character set.

    • An index_col_name specification can end with ASC or DESC. These keywords are allowed for future extensions for specifying ascending or descending index value storage. Currently, they are parsed but ignored; index values are always stored in ascending order.

    • When you use ORDER BY or GROUP BY on a TEXT or BLOB column in a SELECT, the server sorts values using only the initial number of bytes indicated by the max_sort_length system variable. See Section 10.4.3, “The BLOB and TEXT Types”.

    • You can create special FULLTEXT indexes, which are used for full-text searches. Only the MyISAM storage engine supports FULLTEXT indexes. They can be created only from CHAR, VARCHAR, and TEXT columns. Indexing always happens over the entire column; column prefix indexing is not supported and any prefix length is ignored if specified. See Section 11.8, “Full-Text Search Functions”, for details of operation. A WITH PARSER clause can be specified as an index_option value to associate a parser plugin with the index if full-text indexing and searching operations need special handling. This clause is legal only for FULLTEXT indexes. See Section 22.2, “The MySQL Plugin API”, for details on creating plugins.

    • You can create SPATIAL indexes on spatial data types. Spatial types are supported only for MyISAM tables and indexed columns must be declared as NOT NULL. See Section 11.13, “Spatial Extensions”.

    • InnoDB tables support checking of foreign key constraints. See Section 13.6, “The InnoDB Storage Engine”. Note that the FOREIGN KEY syntax in InnoDB is more restrictive than the syntax presented for the CREATE TABLE statement at the beginning of this section: The columns of the referenced table must always be explicitly named. InnoDB supports both ON DELETE and ON UPDATE actions on foreign keys. For the precise syntax, see Section, “FOREIGN KEY Constraints”.

      For other storage engines, MySQL Server parses and ignores the FOREIGN KEY and REFERENCES syntax in CREATE TABLE statements. The CHECK clause is parsed but ignored by all storage engines. See Section, “Foreign Keys”.


      For users familiar with the ANSI/ISO SQL Standard, please note that no storage engine, including InnoDB, recognizes or enforces the MATCH clause used in referential integrity constraint definitions. Use of an explicit MATCH clause will not have the specified effect, and also causes ON DELETE and ON UPDATE clauses to be ignored. For these reasons, specifying MATCH should be avoided.

      The MATCH clause in the SQL standard controls how NULL values in a composite (multiple-column) foreign key are handled when comparing to a primary key. InnoDB essentially implements the semantics defined by MATCH SIMPLE, which allow a foreign key to be all or partially NULL. In that case, the (child table) row containing such a foreign key is allowed to be inserted, and does not match any row in the referenced (parent) table. It is possible to implement other semantics using triggers.

      Additionally, MySQL and InnoDB require that the referenced columns be indexed for performance. However, the system does not enforce a requirement that the referenced columns be UNIQUE or be declared NOT NULL. The handling of foreign key references to nonunique keys or keys that contain NULL values is not well defined for operations such as UPDATE or DELETE CASCADE. You are advised to use foreign keys that reference only UNIQUE and NOT NULL keys.

      Furthermore, InnoDB does not recognize or support “inline REFERENCES specifications” (as defined in the SQL standard) where the references are defined as part of the column specification. InnoDB accepts REFERENCES clauses only when specified as part of a separate FOREIGN KEY specification. For other storage engines, MySQL Server parses and ignores foreign key specifications.


      Partitioned tables do not support foreign keys. See Section 18.5, “Restrictions and Limitations on Partitioning”, for more information.

    • There is a hard limit of 4096 columns per table, but the effective maximum may be less for a given table and depends on the factors discussed in Section D.7.2, “The Maximum Number of Columns Per Table”.

    The TABLESPACE and STORAGE table options were both introduced in MySQL 5.1.6. In MySQL 5.1, they are employed only with NDBCLUSTER tables. The tablespace named tablespace_name must already have been created using CREATE TABLESPACE. STORAGE determines the type of storage used (disk or memory), and can be one of DISK, MEMORY, or DEFAULT.

    TABLESPACE ... STORAGE DISK assigns a table to a MySQL Cluster Disk Data tablespace. See Section 17.5.10, “MySQL Cluster Disk Data Tables”, for more information.


    A STORAGE clause cannot be used in a CREATE TABLE statement without a TABLESPACE clause.

    The ENGINE table option specifies the storage engine for the table.

    The ENGINE table option takes the storage engine names shown in the following table.

    Storage Engine Description
    ARCHIVE The archiving storage engine. See Section 13.12, “The ARCHIVE Storage Engine”.
    CSV Tables that store rows in comma-separated values format. See Section 13.13, “The CSV Storage Engine”.
    EXAMPLE An example engine. See Section 13.10, “The EXAMPLE Storage Engine”.
    FEDERATED Storage engine that accesses remote tables. See Section 13.11, “The FEDERATED Storage Engine”.
    HEAP This is a synonym for MEMORY.
    ISAM (OBSOLETE) Not available in MySQL 5.1. If you are upgrading to MySQL 5.1 from a previous version, you should convert any existing ISAM tables to MyISAM before performing the upgrade.
    InnoDB Transaction-safe tables with row locking and foreign keys. See Section 13.6, “The InnoDB Storage Engine”.
    MEMORY The data for this storage engine is stored only in memory. See Section 13.9, “The MEMORY (HEAP) Storage Engine”.
    MERGE A collection of MyISAM tables used as one table. Also known as MRG_MyISAM. See Section 13.8, “The MERGE Storage Engine”.
    MyISAM The binary portable storage engine that is the default storage engine used by MySQL. See Section 13.5, “The MyISAM Storage Engine”.
    NDBCLUSTER Clustered, fault-tolerant, memory-based tables. Also known as NDB. See Chapter 17, MySQL Cluster NDB 6.X/7.X.

    If a storage engine is specified that is not available, MySQL uses the default engine instead. Normally, this is MyISAM. For example, if a table definition includes the ENGINE=INNODB option but the MySQL server does not support INNODB tables, the table is created as a MyISAM table. This makes it possible to have a replication setup where you have transactional tables on the master but tables created on the slave are nontransactional (to get more speed). In MySQL 5.1, a warning occurs if the storage engine specification is not honored.

    Engine substitution can be controlled by the setting of the NO_ENGINE_SUBSTITUTION SQL mode, as described in Section 5.1.7, “Server SQL Modes”.


    The older TYPE option was synonymous with ENGINE. TYPE has been deprecated since MySQL 4.0 but is still supported for backward compatibility in MySQL 5.1 (excepting MySQL 5.1.7). Since MySQL 5.1.8, it produces a warning. It is removed in MySQL 5.5. You should not use TYPE in any new applications, and you should immediately begin conversion of existing applications to use ENGINE instead. (See Section C.1.46, “Changes in MySQL 5.1.8 (Not released)”.)

    The other table options are used to optimize the behavior of the table. In most cases, you do not have to specify any of them. These options apply to all storage engines unless otherwise indicated. Options that do not apply to a given storage engine may be accepted and remembered as part of the table definition. Such options then apply if you later use ALTER TABLE to convert the table to use a different storage engine.


      The initial AUTO_INCREMENT value for the table. In MySQL 5.1, this works for MyISAM, MEMORY, and InnoDB tables. It also works for ARCHIVE tables as of MySQL 5.1.6. To set the first auto-increment value for engines that do not support the AUTO_INCREMENT table option, insert a “dummy” row with a value one less than the desired value after creating the table, and then delete the dummy row.

      For engines that support the AUTO_INCREMENT table option in CREATE TABLE statements, you can also use ALTER TABLE tbl_name AUTO_INCREMENT = N to reset the AUTO_INCREMENT value. The value cannot be set lower than the maximum value currently in the column.


      An approximation of the average row length for your table. You need to set this only for large tables with variable-size rows.

      When you create a MyISAM table, MySQL uses the product of the MAX_ROWS and AVG_ROW_LENGTH options to decide how big the resulting table is. If you don't specify either option, the maximum size for MyISAM data and index files is 256TB by default. (If your operating system does not support files that large, table sizes are constrained by the file size limit.) If you want to keep down the pointer sizes to make the index smaller and faster and you don't really need big files, you can decrease the default pointer size by setting the myisam_data_pointer_size system variable. (See Section 5.1.4, “Server System Variables”.) If you want all your tables to be able to grow above the default limit and are willing to have your tables slightly slower and larger than necessary, you can increase the default pointer size by setting this variable. Setting the value to 7 allows table sizes up to 65,536TB.


      Specify a default character set for the table. CHARSET is a synonym for CHARACTER SET. If the character set name is DEFAULT, the database character set is used.


      Set this to 1 if you want MySQL to maintain a live checksum for all rows (that is, a checksum that MySQL updates automatically as the table changes). This makes the table a little slower to update, but also makes it easier to find corrupted tables. The CHECKSUM TABLE statement reports the checksum. (MyISAM only.)


      Specify a default collation for the table.


      A comment for the table, up to 60 characters long.


      The connection string for a FEDERATED table.


      Older versions of MySQL used a COMMENT option for the connection string.


      By using DATA DIRECTORY='directory' or INDEX DIRECTORY='directory' you can specify where the MyISAM storage engine should put a table's data file and index file. The directory must be the full path name to the directory, not a relative path.


      Beginning with MySQL 5.1.23, table-level DATA DIRECTORY and INDEX DIRECTORY options are ignored for partitioned tables. (Bug#32091)

      These options work only when you are not using the --skip-symbolic-links option. Your operating system must also have a working, thread-safe realpath() call. See Section, “Using Symbolic Links for Tables on Unix”, for more complete information.

      If a MyISAM table is created with no DATA DIRECTORY option, the .MYD file is created in the database directory. By default, if MyISAM finds an existing .MYD file in this case, it overwrites it. The same applies to .MYI files for tables created with no INDEX DIRECTORY option. As of MySQL 5.1.23, to suppress this behavior, start the server with the --keep_files_on_create option, in which case MyISAM will not overwrite existing files and returns an error instead.

      If a MyISAM table is created with a DATA DIRECTORY or INDEX DIRECTORY option and an existing .MYD or .MYI file is found, MyISAM always returns an error. It will not overwrite a file in the specified directory.


      Beginning with MySQL 5.1.24, you cannot use path names that contain the MySQL data directory with DATA DIRECTORY or INDEX DIRECTORY. This includes partitioned tables and individual table partitions. (See Bug#32167.)


      Set this to 1 if you want to delay key updates for the table until the table is closed. See the description of the delay_key_write system variable in Section 5.1.4, “Server System Variables”. (MyISAM only.)


      If you want to insert data into a MERGE table, you must specify with INSERT_METHOD the table into which the row should be inserted. INSERT_METHOD is an option useful for MERGE tables only. Use a value of FIRST or LAST to have inserts go to the first or last table, or a value of NO to prevent inserts. See Section 13.8, “The MERGE Storage Engine”.


      This option provides a hint to the storage engine about the size in bytes to use for index key blocks. The engine is allowed to change the value if necessary. A value of 0 indicates that the default value should be used. Individual index definitions can specify a KEY_BLOCK_SIZE value of their own to override the table value. KEY_BLOCK_SIZE was added in MySQL 5.1.10.

    • MAX_ROWS

      The maximum number of rows you plan to store in the table. This is not a hard limit, but rather a hint to the storage engine that the table must be able to store at least this many rows.

    • MIN_ROWS

      The minimum number of rows you plan to store in the table. The MEMORY storage engine uses this option as a hint about memory use.


      PACK_KEYS takes effect only with MyISAM tables. Set this option to 1 if you want to have smaller indexes. This usually makes updates slower and reads faster. Setting the option to 0 disables all packing of keys. Setting it to DEFAULT tells the storage engine to pack only long CHAR, VARCHAR, BINARY, or VARBINARY columns.

      If you do not use PACK_KEYS, the default is to pack strings, but not numbers. If you use PACK_KEYS=1, numbers are packed as well.

      When packing binary number keys, MySQL uses prefix compression:

      • Every key needs one extra byte to indicate how many bytes of the previous key are the same for the next key.

      • The pointer to the row is stored in high-byte-first order directly after the key, to improve compression.

      This means that if you have many equal keys on two consecutive rows, all following “same” keys usually only take two bytes (including the pointer to the row). Compare this to the ordinary case where the following keys takes storage_size_for_key + pointer_size (where the pointer size is usually 4). Conversely, you get a significant benefit from prefix compression only if you have many numbers that are the same. If all keys are totally different, you use one byte more per key, if the key is not a key that can have NULL values. (In this case, the packed key length is stored in the same byte that is used to mark if a key is NULL.)


      This option is unused. If you have a need to scramble your .frm files and make them unusable to any other MySQL server, please contact our sales department.


      RAID support has been removed as of MySQL 5.0. For information on RAID, see CREATE TABLE Syntax.


      Defines how the rows should be stored. For MyISAM tables, the option value can be FIXED or DYNAMIC for static or variable-length row format. myisampack sets the type to COMPRESSED. See Section 13.5.3, “MyISAM Table Storage Formats”.

      For InnoDB tables, rows are stored in compact format (ROW_FORMAT=COMPACT) by default. The noncompact format used in older versions of MySQL can still be requested by specifying ROW_FORMAT=REDUNDANT.


      When executing a CREATE TABLE statement, if you specify a row format which is not supported by the storage engine that is used for the table, the table is created using that storage engine's default row format. The information reported in this column in response to SHOW TABLE STATUS is the actual row format used. This may differ from the value in the Create_options column because the original CREATE TABLE definition is retained during creation.

    • UNION

      UNION is used when you want to access a collection of identical MyISAM tables as one. This works only with MERGE tables. See Section 13.8, “The MERGE Storage Engine”.

      You must have SELECT, UPDATE, and DELETE privileges for the tables you map to a MERGE table.


      Formerly, all tables used had to be in the same database as the MERGE table itself. This restriction no longer applies.

    partition_options can be used to control partitioning of the table created with CREATE TABLE.


    Not all options shown in the syntax for partition_options at the beginning of this section are available for all partitioning types. Please see the listings for the following individual types for information specific to each type, and see Chapter 18, Partitioning, for more complete information about the workings of and uses for partitioning in MySQL, as well as additional examples of table creation and other statements relating to MySQL partitioning.

    If used, a partition_options clause begins with PARTITION BY. This clause contains the function that is used to determine the partition; the function returns an integer value ranging from 1 to num, where num is the number of partitions. (The maximum number of user-defined partitions which a table may contain is 1024; the number of subpartitions—discussed later in this section—is included in this maximum.) The choices that are available for this function in MySQL 5.1 are shown in the following list:

    • HASH(expr): Hashes one or more columns to create a key for placing and locating rows. expr is an expression using one or more table columns. This can be any legal MySQL expression (including MySQL functions) that yields a single integer value. For example, these are all valid CREATE TABLE statements using PARTITION BY HASH:

      CREATE TABLE t1 (col1 INT, col2 CHAR(5))
          PARTITION BY HASH(col1);
      CREATE TABLE t1 (col1 INT, col2 CHAR(5))
          PARTITION BY HASH( ORD(col2) );
      CREATE TABLE t1 (col1 INT, col2 CHAR(5), col3 DATETIME)
          PARTITION BY HASH ( YEAR(col3) );

      You may not use either VALUES LESS THAN or VALUES IN clauses with PARTITION BY HASH.

      PARTITION BY HASH uses the remainder of expr divided by the number of partitions (that is, the modulus). For examples and additional information, see Section 18.2.3, “HASH Partitioning”.

      The LINEAR keyword entails a somewhat different algorithm. In this case, the number of the partition in which a row is stored is calculated as the result of one or more logical AND operations. For discussion and examples of linear hashing, see Section, “LINEAR HASH Partitioning”.

    • KEY(column_list): This is similar to HASH, except that MySQL supplies the hashing function so as to guarantee an even data distribution. The column_list argument is simply a list of table columns. This example shows a simple table partitioned by key, with 4 partitions:

      CREATE TABLE tk (col1 INT, col2 CHAR(5), col3 DATE)
          PARTITION BY KEY(col3)
          PARTITIONS 4;

      For tables that are partitioned by key, you can employ linear partitioning by using the LINEAR keyword. This has the same effect as with tables that are partitioned by HASH. That is, the partition number is found using the & operator rather than the modulus (see Section, “LINEAR HASH Partitioning”, and Section 18.2.4, “KEY Partitioning”, for details). This example uses linear partitioning by key to distribute data between 5 partitions:

      CREATE TABLE tk (col1 INT, col2 CHAR(5), col3 DATE)
          PARTITIONS 5;

      You may not use either VALUES LESS THAN or VALUES IN clauses with PARTITION BY KEY.

    • RANGE: In this case, expr shows a range of values using a set of VALUES LESS THAN operators. When using range partitioning, you must define at least one partition using VALUES LESS THAN. You cannot use VALUES IN with range partitioning.

      VALUES LESS THAN can be used with either a literal value or an expression that evaluates to a single value.

      Suppose that you have a table that you wish to partition on a column containing year values, according to the following scheme.

      Partition Number: Years Range:
      0 1990 and earlier
      1 1991 to 1994
      2 1995 to 1998
      3 1999 to 2002
      4 2003 to 2005
      5 2006 and later

      A table implementing such a partitioning scheme can be realized by the CREATE TABLE statement shown here:

      CREATE TABLE t1 (
          year_col  INT,
          some_data INT
      PARTITION BY RANGE (year_col) (
          PARTITION p0 VALUES LESS THAN (1991),
          PARTITION p1 VALUES LESS THAN (1995),
          PARTITION p2 VALUES LESS THAN (1999),
          PARTITION p3 VALUES LESS THAN (2002),
          PARTITION p4 VALUES LESS THAN (2006),

      PARTITION ... VALUES LESS THAN ... statements work in a consecutive fashion. VALUES LESS THAN MAXVALUE works to specify “leftover” values that are greater than the maximum value otherwise specified.

      Note that VALUES LESS THAN clauses work sequentially in a manner similar to that of the case portions of a switch ... case block (as found in many programming languages such as C, Java, and PHP). That is, the clauses must be arranged in such a way that the upper limit specified in each successive VALUES LESS THAN is greater than that of the previous one, with the one referencing MAXVALUE coming last of all in the list.

    • LIST(expr): This is useful when assigning partitions based on a table column with a restricted set of possible values, such as a state or country code. In such a case, all rows pertaining to a certain state or country can be assigned to a single partition, or a partition can be reserved for a certain set of states or countries. It is similar to RANGE, except that only VALUES IN may be used to specify allowable values for each partition.

      VALUES IN is used with a list of values to be matched. For instance, you could create a partitioning scheme such as the following:

      CREATE TABLE client_firms (
          id   INT,
          name VARCHAR(35)
      PARTITION BY LIST (id) (
          PARTITION r0 VALUES IN (1, 5, 9, 13, 17, 21),
          PARTITION r1 VALUES IN (2, 6, 10, 14, 18, 22),
          PARTITION r2 VALUES IN (3, 7, 11, 15, 19, 23),
          PARTITION r3 VALUES IN (4, 8, 12, 16, 20, 24)

      When using list partitioning, you must define at least one partition using VALUES IN. You cannot use VALUES LESS THAN with PARTITION BY LIST.


      Currently, the value list used with VALUES IN must consist of integer values only.

    • The number of partitions may optionally be specified with a PARTITIONS num clause, where num is the number of partitions. If both this clause and any PARTITION clauses are used, num must be equal to the total number of any partitions that are declared using PARTITION clauses.


      Whether or not you use a PARTITIONS clause in creating a table that is partitioned by RANGE or LIST, you must still include at least one PARTITION VALUES clause in the table definition (see below).

    • A partition may optionally be divided into a number of subpartitions. This can be indicated by using the optional SUBPARTITION BY clause. Subpartitioning may be done by HASH or KEY. Either of these may be LINEAR. These work in the same way as previously described for the equivalent partitioning types. (It is not possible to subpartition by LIST or RANGE.)

      The number of subpartitions can be indicated using the SUBPARTITIONS keyword followed by an integer value.

    • MySQL 5.1.12 introduces rigorous checking of the value used in a PARTITIONS or SUBPARTITIONS clause. Beginning with this version, this value must adhere to the following rules:

      • The value must be a positive, nonzero integer.

      • No leading zeros are permitted.

      • The value must be an integer literal, and cannot not be an expression. For example, PARTITIONS 0.2E+01 is not allowed, even though 0.2E+01 evaluates to 2. (Bug#15890)


    The expression (expr) used in a PARTITION BY clause cannot refer to any columns not in the table being created; beginning with MySQL 5.1.23, such references are specifically disallowed and cause the statement to fail with an error. (Bug#29444)

    Each partition may be individually defined using a partition_definition clause. The individual parts making up this clause are as follows:

    • PARTITION partition_name: This specifies a logical name for the partition.

    • A VALUES clause: For range partitioning, each partition must include a VALUES LESS THAN clause; for list partitioning, you must specify a VALUES IN clause for each partition. This is used to determine which rows are to be stored in this partition. See the discussions of partitioning types in Chapter 18, Partitioning, for syntax examples.

    • An optional COMMENT clause may be used to specify a string that describes the partition. Example:

      COMMENT = 'Data for the years previous to 1999'
    • DATA DIRECTORY and INDEX DIRECTORY may be used to indicate the directory where, respectively, the data and indexes for this partition are to be stored. Both the data_dir and the index_dir must be absolute system path names. Example:

      CREATE TABLE th (id INT, name VARCHAR(30), adate DATE)
        PARTITION p1999 VALUES IN (1995, 1999, 2003)
          DATA DIRECTORY = '/var/appdata/95/data'
          INDEX DIRECTORY = '/var/appdata/95/idx',
        PARTITION p2000 VALUES IN (1996, 2000, 2004)
          DATA DIRECTORY = '/var/appdata/96/data'
          INDEX DIRECTORY = '/var/appdata/96/idx',
        PARTITION p2001 VALUES IN (1997, 2001, 2005)
          DATA DIRECTORY = '/var/appdata/97/data'
          INDEX DIRECTORY = '/var/appdata/97/idx',
        PARTITION p2000 VALUES IN (1998, 2002, 2006)
          DATA DIRECTORY = '/var/appdata/98/data'
          INDEX DIRECTORY = '/var/appdata/98/idx'

      DATA DIRECTORY and INDEX DIRECTORY behave in the same way as in the CREATE TABLE statement's table_option clause as used for MyISAM tables.

      One data directory and one index directory may be specified per partition. If left unspecified, the data and indexes are stored by default in the table's database directory.

      On Windows, the DATA DIRECTORY and INDEX DIRECTORY options are not supported for individual partitions or subpartitions. Beginning with MySQL 5.1.24, these options are ignored on Windows, except that a warning is generated. (Bug#30459)


      Prior to MySQL 5.1.18, DATA DIRECTORY and INDEX DIRECTORY were allowed even if the NO_DIR_IN_CREATE server SQL mode was in effect at the time that a partitioned table was created. Beginning with MySQL 5.1.18, these options are ignored for creating partitioned tables if NO_DIR_IN_CREATE is in effect. (Bug#24633)

    • MAX_ROWS and MIN_ROWS may be used to specify, respectively, the maximum and minimum number of rows to be stored in the partition. The values for max_number_of_rows and min_number_of_rows must be positive integers. As with the table-level options with the same names, these act only as “suggestions” to the server and are not hard limits.

    • The optional TABLESPACE clause may be used to designate a tablespace for the partition. Used for MySQL Cluster only.

    • The partitioning handler accepts a [STORAGE] ENGINE option for both PARTITION and SUBPARTITION. Currently, the only way in which this can be used is to set all partitions or all subpartitions to the same storage engine, and an attempt to set different storage engines for partitions or subpartitions in the same table will give rise to the error ERROR 1469 (HY000): The mix of handlers in the partitions is not allowed in this version of MySQL. We expect to lift this restriction on partitioning in a future MySQL release.

    • The NODEGROUP option can be used to make this partition act as part of the node group identified by node_group_id. This option is applicable only to MySQL Cluster.

    • The partition definition may optionally contain one or more subpartition_definition clauses. Each of these consists at a minimum of the SUBPARTITION name, where name is an identifier for the subpartition. Except for the replacement of the PARTITION keyword with SUBPARTITION, the syntax for a subpartition definition is identical to that for a partition definition.

      Subpartitioning must be done by HASH or KEY, and can be done only on RANGE or LIST partitions. See Section 18.2.5, “Subpartitioning”.

    Partitions can be modified, merged, added to tables, and dropped from tables. For basic information about the MySQL statements to accomplish these tasks, see Section 12.1.7, “ALTER TABLE Syntax”. For more detailed descriptions and examples, see Section 18.3, “Partition Management”.


    The original CREATE TABLE statement, including all specifications and table options are stored by MySQL when the table is created. The information is retained so that if you change storage engines, collations or other settings using an ALTER TABLE statement, the original table options specified are retained. This allows you to change between InnoDB and MyISAM table types even though the row formats supported by the two engines are different.

    Because the text of the original statement is retained, but due to the way that certain values and options may be silently reconfigured (such as the ROW_FORMAT), the active table definition (accessible through DESCRIBE or with SHOW TABLE STATUS) and the table creation string (accessible through SHOW CREATE TABLE) will report different values.

    You can create one table from another by adding a SELECT statement at the end of the CREATE TABLE statement:

    CREATE TABLE new_tbl SELECT * FROM orig_tbl;

    MySQL creates new columns for all elements in the SELECT. For example:

        ->        PRIMARY KEY (a), KEY(b))
        ->        ENGINE=MyISAM SELECT b,c FROM test2;

    This creates a MyISAM table with three columns, a, b, and c. Notice that the columns from the SELECT statement are appended to the right side of the table, not overlapped onto it. Take the following example:

    mysql> SELECT * FROM foo;
    | n |
    | 1 |
    mysql> CREATE TABLE bar (m INT) SELECT n FROM foo;
    Query OK, 1 row affected (0.02 sec)
    Records: 1  Duplicates: 0  Warnings: 0
    mysql> SELECT * FROM bar;
    | m    | n |
    | NULL | 1 |
    1 row in set (0.00 sec)

    For each row in table foo, a row is inserted in bar with the values from foo and default values for the new columns.

    In a table resulting from CREATE TABLE ... SELECT, columns named only in the CREATE TABLE part come first. Columns named in both parts or only in the SELECT part come after that. The data type of SELECT columns can be overridden by also specifying the column in the CREATE TABLE part.

    If any errors occur while copying the data to the table, it is automatically dropped and not created.

    CREATE TABLE ... SELECT does not automatically create any indexes for you. This is done intentionally to make the statement as flexible as possible. If you want to have indexes in the created table, you should specify these before the SELECT statement:

    mysql> CREATE TABLE bar (UNIQUE (n)) SELECT n FROM foo;

    Some conversion of data types might occur. For example, the AUTO_INCREMENT attribute is not preserved, and VARCHAR columns can become CHAR columns. Retrained attributes are NULL (or NOT NULL) and, for those columns that have them, CHARACTER SET, COLLATION, COMMENT, and the DEFAULT clause.

    When creating a table with CREATE ... SELECT, make sure to alias any function calls or expressions in the query. If you do not, the CREATE statement might fail or result in undesirable column names.

    CREATE TABLE artists_and_works
      SELECT artist.name, COUNT(work.artist_id) AS number_of_works
      FROM artist LEFT JOIN work ON artist.id = work.artist_id
      GROUP BY artist.id;

    You can also explicitly specify the data type for a generated column:


    For CREATE TABLE ... SELECT, if IF NOT EXISTS is given and the table already exists, MySQL handles the statement as follows:

    • The table definition given in the CREATE TABLE part is ignored. No error occurs, even if the definition does not match that of the existing table.

    • If there is a mismatch between the number of columns in the table and the number of columns produced by the SELECT part, the selected values are assigned to the rightmost columns. For example, if the table contains n columns and the SELECT produces m columns, where m < n, the selected values are assigned to the m rightmost columns in the table. Each of the initial nm columns is assigned its default value, either that specified explicitly in the column definition or the implicit column data type default if the definition contains no default. If the SELECT part produces too many columns (m > n), an error occurs.

    • If strict SQL mode is enabled and any of these initial columns do not have an explicit default value, the statement fails with an error.

    The following example illustrates IF NOT EXISTS handling:

    mysql> CREATE TABLE t1 (i1 INT DEFAULT 0, i2 INT, i3 INT, i4 INT);
    Query OK, 0 rows affected (0.05 sec)
    mysql> CREATE TABLE IF NOT EXISTS t1 (c1 CHAR(10)) SELECT 1, 2;
    Query OK, 1 row affected, 1 warning (0.01 sec)
    Records: 1  Duplicates: 0  Warnings: 0
    mysql> SELECT * FROM t1;
    | i1   | i2   | i3   | i4   |
    |    0 | NULL |    1 |    2 |
    1 row in set (0.00 sec)

    Use LIKE to create an empty table based on the definition of another table, including any column attributes and indexes defined in the original table:

    CREATE TABLE new_tbl LIKE orig_tbl;

    The copy is created using the same version of the table storage format as the original table. The SELECT privilege is required on the original table.

    LIKE works only for base tables, not for views.

    CREATE TABLE ... LIKE does not preserve any DATA DIRECTORY or INDEX DIRECTORY table options that were specified for the original table, or any foreign key definitions.

    If the original table is a TEMPORARY table, CREATE TABLE ... LIKE does not preserve TEMPORARY. To create a TEMPORARY destination table, use CREATE TEMPORARY TABLE ... LIKE.

    You can precede the SELECT by IGNORE or REPLACE to indicate how to handle rows that duplicate unique key values. With IGNORE, new rows that duplicate an existing row on a unique key value are discarded. With REPLACE, new rows replace rows that have the same unique key value. If neither IGNORE nor REPLACE is specified, duplicate unique key values result in an error.

    To ensure that the binary log can be used to re-create the original tables, MySQL does not allow concurrent inserts during CREATE TABLE ... SELECT.