How to copy a row n times in sqlite? - sql

Question

For a load test I have to copy a row in my table in a sqlite database 1000 (5000, 10000) times.
With the statement
INSERT INTO MYTABLE (
created,
modified,
anotherfield,
etc
)
SELECT created,
modified,
anotherfield,
etc FROM MYTABLE WHERE id = 1;
I can copy it one time. But it would be great to be able to put this into a loop to execute this statement n times.
It seems like SQLite does not support for-loops. I found something called WITH RECURSIVE which could be something like the SQLite way to handle loops. But if I execute
WITH RECURSIVE
cnt(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM cnt WHERE x<1000)
<insert_statement_from_above>
the insert statement gets executed only once.
What am I doing wrong? How can I get to insert 1000 (5000, 10000) rows without having to add them all one by one? Thanks!

Answer 1

You must CROSS join the table to the recursive cte to produce 1000 rows:
WITH RECURSIVE cte(x) AS (SELECT 1 UNION ALL SELECT x + 1 FROM cte WHERE x < 1000)
INSERT INTO MYTABLE (created, modified, anotherfield)
SELECT m.created, m.modified, m.anotherfield
FROM MYTABLE m CROSS JOIN cte c
WHERE m.id = 1;
See the demo (for 3 rows).
Another way to use the recursive cte:
WITH RECURSIVE cte AS (
SELECT created, modified, anotherfield, 1 x
FROM MYTABLE
WHERE id = 1
UNION ALL
SELECT created, modified, anotherfield, x + 1
FROM cte
WHERE x < 1000
)
INSERT INTO MYTABLE (created, modified, anotherfield)
SELECT created, modified, anotherfield
FROM cte;
See the demo.