EXCEPT
MariaDB starting with 10.3.0
EXCEPT was introduced in MariaDB 10.3.0.
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}]
Contents
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.
MariaDB starting with 10.4.0
Parentheses
From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned.
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 | +------+