UNION
Warning
SingleStore 9.0 gives you the opportunity to preview, evaluate, and provide feedback on new and upcoming features prior to their general availability. In the interim, SingleStore 8.9 is recommended for production workloads, which can later be upgraded to SingleStore 9.0.
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Combines results from multiple SELECT statements.
UNION DISTINCT
removes duplicate rows, while UNION ALL
does not remove them.UNION
is equivalent to UNION DISTINCT
.
Syntax
SELECT ...
UNION [ALL | DISTINCT] SELECT ...
[UNION [ALL | DISTINCT] SELECT ...]
Remarks
-
The first and all subsequent
SELECT
statements must select the same number of columns. -
UNION
statements are converted into nested sub-select queries by the query processor. -
The maximum depth of nested sub-select queries is 40.
Beyond this the UNION
statements are converted toTABLE
, allowing you to write up to 337 statements (0-336).
Examples
SELECT * FROM table_a UNION ALL SELECT * FROM table_b;SELECT * FROM table_a UNION SELECT * FROM table_b;
SELECT * FROM id_t UNION ALL SELECT * FROM id_t2;
+------+----------------------------------------------------------------------------+
| a | b |
+------+----------------------------------------------------------------------------+
| 1 | 0xE82C75FA86974BE7903270F4353D865C |
| 1 | 0x31343865306665352D666666322D346363362D383634622D313838303637313135653236 |
+------+----------------------------------------------------------------------------+
Last modified: March 31, 2025