The result of EXCEPT is all records of the left SELECT result set except records which are in right SELECT result set, i.e. it is subtraction of two result sets.

Syntax

SELECT ...
(INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ...
[(INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

Please note:

• ALL is not supported by EXCEPT (and it is difficult to make sense of ALL with EXCEPT).
• Brackets for explicit operation precedence are not supported; use a subquery in the FROM clause as a workaround).

Description

MariaDB has supported EXCEPT and INTERSECT in addition to UNION since MariaDB 10.3.

All behavior for naming columns, ORDER BY and LIMIT is the same as for UNION.

EXCEPT implicitly supposes a DISTINCT operation.

The result of EXCEPT is all records of the left SELECT result except records which are in right SELECT result set, i.e. it is subtraction of two result sets.

EXCEPT and UNION have the same operation precedence.

Examples

Show customers which are not employees:

(SELECT e_name AS name, email FROM customers)
EXCEPT
(SELECT c_name AS name, email FROM employees);

Difference between UNION, EXCEPT and INTERSECT:

CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(3),(4),(5),(6);

SELECT i FROM seqs WHERE i <= 3 UNION SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
+------+

Parentheses for specifying precedence, from MariaDB 10.4.0

CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);

INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);

((SELECT a FROM t1) UNION (SELECT b FROM t2)) EXCEPT (SELECT c FROM t3);
+------+
| a    |
+------+
|    2 |
|    3 |
|    4 |
|    5 |
+------+

(SELECT a FROM t1) UNION ((SELECT b FROM t2) EXCEPT (SELECT c FROM t3));
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
+------+

See Also

• UNION
• INTERSECT