create table t1 (i int);

insert into t1 values (1),(2),(3);

(select * from t1);                                      #this works

(with cte as (select * from t1) select * from cte);      #but this returns syntax error

with cte as (select * from t1) (select * from cte UNION select * from t1);

with cte as (select * from t1) (select * from cte UNION select * from t1) LIMIT 1;

MariaDB [test]> create table t1 (i int);

Query OK, 0 rows affected (0.166 sec)

MariaDB [test]> insert into t1 values (1),(2),(3);

Query OK, 3 rows affected (0.025 sec)

Records: 3  Duplicates: 0  Warnings: 0

MariaDB [test]> (select * from t1);

+------+

| i    |

+------+

|    1 |

|    2 |

|    3 |

+------+

3 rows in set (0.000 sec)

MariaDB [test]> (with cte as (select * from t1) select * from cte);

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 'with cte as (select * from t1) select * from cte)' at line 1

MariaDB [test]> with cte as (select * from t1) (select * from cte 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

MariaDB [test]> with cte as (select * from t1) (select * from cte UNION select * 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 'UNION select * from t1) LIMIT 1' at line 1