Precedence Control in Table Operations

Syntax

(  expression )
[ORDER BY [column[, column...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

Description

Using parentheses in your SQL allows you to control the order of execution for SELECT statements and Table Value Constructor, including UNION, EXCEPT, and INTERSECT operations. MariaDB executes the parenthetical expression before the rest of the statement. You can then use ORDER BY and LIMIT clauses the further organize the result-set.

Example

CREATE TABLE test.t1 (num INT);

INSERT INTO test.t1 VALUES (1),(2),(3);

(SELECT * FROM test.t1 
 UNION 
 VALUES (10)) 
INTERSECT 
VALUES (1),(3),(10),(11);
+------+
| num  |
+------+
|    1 |
|    3 |
|   10 |
+------+

((SELECT * FROM test.t1 
  UNION 
  VALUES (10)) 
 INTERSECT 
 VALUES (1),(3),(10),(11)) 
ORDER BY 1 DESC;
+------+
| num  |
+------+
|   10 |
|    3 |
|    1 |
+------+