Postgres 14

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     CREATE TABLE test ( id SERIAL, a VARCHAR(10), b VARCHAR(10) );

    INSERT INTO test ( a, b )
        WITH RECURSIVE Numbers(i) AS (
               SELECT 1
            UNION ALL
               SELECT i + 1
                 FROM Numbers
                WHERE i < 5 -- this is the value `x`
        )
             SELECT adhoc.*
               FROM Numbers n
         CROSS JOIN ( -- This is the single record to be inserted multiple times
                       SELECT 'value_a' a
                            , 'value_b' b
                    ) adhoc
     ;
5 rows affected

      SELECT * FROM test;


id
a
b


1
value_a
value_b

2
value_a
value_b

3
value_a
value_b

4
value_a
value_b

5
value_a
value_b

id	a	b
1	value_a	value_b
2	value_a	value_b
3	value_a	value_b
4	value_a	value_b
5	value_a	value_b