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MySQL 8.0 Reference Manual  /  ...  /  CREATE TEMPORARY TABLE Syntax

Pre-General Availability Draft: 2017-05-29

14.1.15.3 CREATE TEMPORARY TABLE Syntax

You can use the TEMPORARY keyword when creating a table. A TEMPORARY table is visible only to the current session, and is dropped automatically when the session is closed. This means that two different sessions 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.)

InnoDB does not support compressed temporary tables. When innodb_strict_mode is enabled (the default), CREATE TEMPORARY TABLE returns an error if ROW_FORMAT=COMPRESSED or KEY_BLOCK_SIZE is specified. If innodb_strict_mode is disabled, warnings are issued and the temporary table is created using a non-compressed row format. InnoDB temporary tables are created in the shared temporary tablespace, ibtmp1. The innodb_file_per-table option does not affect the creation of InnoDB temporary tables.

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

TEMPORARY tables have a very loose relationship with databases (schemas). Dropping a database does not automatically drop any TEMPORARY tables created within that database. Also, you can create a TEMPORARY table in a nonexistent database if you qualify the table name with the database name in the CREATE TABLE statement. In this case, all subsequent references to the table must be qualified with the database name.

To create a temporary table, you must have the CREATE TEMPORARY TABLES privilege. After a session has created a temporary table, the server performs no further privilege checks on the table. The creating session can perform any operation on the table, such as DROP TABLE, INSERT, UPDATE, or SELECT.

One implication of this behavior is that a session can manipulate its temporary tables even if the current user has no privilege to create them. Suppose that the current user does not have the CREATE TEMPORARY TABLES privilege but is able to execute a DEFINER-context stored procedure that executes with the privileges of a user who does have CREATE TEMPORARY TABLES and that creates a temporary table. While the procedure executes, the session uses the privileges of the defining user. After the procedure returns, the effective privileges revert to those of the current user, which can still see the temporary table and perform any operation on it.

As of MySQL 8.0.2, you cannot use CREATE TEMPORY TABLE ... LIKE to create an empty table based on the definition of a table that resides in the mysql tablespace, InnoDB system tablespace (innodb_system), or a general tablespace. The tablespace definition for such a table includes a TABLESPACE attribute that defines the tablespace where the table resides, and the aforementioned tablespaces do not support temporary tables. To create a temporary table based on the definition of such a table, use this syntax instead:

CREATE TEMPORARY TABLE new_tbl SELECT * FROM orig_tbl LIMIT 0;        

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