[#MDEV-10028] Syntax error on ((SELECT ...) UNION (SELECT ...))

I create and populate a table:

DROP TABLE t1;

CREATE TABLE t1 (a INT);

INSERT INTO t1 VALUES (10);

INSERT INTO t1 VALUES (20);

INSERT INTO t1 VALUES (30);

Now I run this SQL Standard compliant query:

((SELECT a FROM t1) UNION (SELECT a FROM t1));

it returns a syntax error:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'UNION (SELECT a FROM t1))' at line 1

PostgreSQL and Oracle work fine on the same query.

This Standard-compliant query also returns a syntax_error:

(SELECT * FROM t1 UNION SELECT * FROM t1);

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'UNION SELECT * FROM t1)' at line 1

PostgreSQL and Oracle work fine on this query.

This query returns a syntax error:

((SELECT a FROM t1) LIMIT 1);

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'LIMIT 1)' at line 1

It should return a result. It works fine in PostreSQL. Also, it is a direct equivalent query to this Standard-compliant version:

((SELECT a FROM t1) FETCH FIRST 1 ROWS ONLY);

Another example:

SELECT * FROM (SELECT 1 UNION (SELECT 2 UNION SELECT 3)) t1;

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'UNION SELECT 3) t1' at line 1

The same query works in PostgreSQL.
A similar query works in Oracle (with FROM DUAL added, and with no derived table alias)

SELECT * FROM (SELECT 1 FROM DUAL UNION (SELECT 2 FROM DUAL UNION SELECT 3 FROM DUAL))

[MDEV-10028] Syntax error on ((SELECT ...) UNION (SELECT ...)) Created: 2016-05-05 Updated: 2018-07-09 Resolved: 2018-07-09
Status:	Closed
Project:	MariaDB Server
Component/s:	Parser
Affects Version/s:	5.5, 10.0, 10.1, 10.2
Fix Version/s:	10.4.0

[MDEV-10028] Syntax error on ((SELECT ...) UNION (SELECT ...)) Created: 2016-05-05 Updated: 2018-07-09 Resolved: 2018-07-09