Temporary tables created with
CREATE TEMPORARY
TABLE
have the following limitations:
TEMPORARY
tables are supported only by theInnoDB
,MEMORY
,MyISAM
, andMERGE
storage engines.Temporary tables are not supported for NDB Cluster.
The
SHOW TABLES
statement does not listTEMPORARY
tables.To rename
TEMPORARY
tables,RENAME TABLE
does not work. UseALTER TABLE
instead:ALTER TABLE old_name RENAME new_name;
You cannot refer to a
TEMPORARY
table more than once in the same query. For example, the following does not work:SELECT * FROM temp_table JOIN temp_table AS t2;
The statement produces this error:
ERROR 1137: Can't reopen table: 'temp_table'
You can work around this issue if your query permits use of a common table expression (CTE) rather than a
TEMPORARY
table. For example, this fails with the Can't reopen table error:CREATE TEMPORARY TABLE t SELECT 1 AS col_a, 2 AS col_b; SELECT * FROM t AS t1 JOIN t AS t2;
To avoid the error, use a
WITH
clause that defines a CTE, rather than theTEMPORARY
table:WITH cte AS (SELECT 1 AS col_a, 2 AS col_b) SELECT * FROM cte AS t1 JOIN cte AS t2;
The Can't reopen table error also occurs if you refer to a temporary table multiple times in a stored function under different aliases, even if the references occur in different statements within the function. It may occur for temporary tables created outside stored functions and referred to across multiple calling and callee functions.
If a
TEMPORARY
is created with the same name as an existing non-TEMPORARY
table, the non-TEMPORARY
table is hidden until theTEMPORARY
table is dropped, even if the tables use different storage engines.There are known issues in using temporary tables with replication. See Section 19.5.1.31, “Replication and Temporary Tables”, for more information.