MySQL INSERT with SELECT UNION gives syntax error

Question

Supposed I have a table SomeTable with a single INT column.

This query works fine:

INSERT INTO SomeTable
(SELECT 1 WHERE true) 
UNION
(SELECT 2 FROM SomeTable WHERE true) 

But this gives a syntax error:

INSERT INTO SomeTable
(SELECT 1 WHERE true) 
UNION
(SELECT 2 WHERE true) 

Error Code: 1064. You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE true)' at line 4

What's the cause of the error?

How else would I insert multiple rows with a WHERE filter?

Answer 1

Remove parentheses and the where clause you have not a FROM clause so your where is not applicable

INSERT INTO SomeTable
SELECT 1 
UNION
SELECT 2 

or if you want a where condition you can use from dual

SELECT 1 from dual WHERE true
union 
SELECT 2 from  dual  WHERE true

Answer 2

Your parenthesis causes the problem. :

INSERT INTO SomeTable (col)
     SELECT 1 
     FROM . . 
     WHERE . . .
     UNION
     SELECT 2 
     FROM SomeTable 
     WHERE . . . ;