Can I run a loop in MySQL without using a procedure/function?

Question

For testing, is it possible to run a loop from MySQL workbench or similar tool? I tried but got an error.

If it is possible, please supply a simple example I can run.

Answer 1

You can't do a for loop in an SQL editor without a stored procedure. I use TOAD for MySQL.

A quick stored procedure should do the job:

DELIMITER $$

DROP PROCEDURE IF EXISTS proc_loop_test$$
CREATE PROCEDURE proc_loop_test()
BEGIN
  DECLARE int_val INT DEFAULT 0;
  test_loop : LOOP
    IF (int_val = 10) THEN
      LEAVE test_loop;
    END IF;

    SET int_val = int_val +1;
    SELECT int_val; 
  END LOOP; 
END$$

DELIMITER ;

Answer 2

Supposed that you already have an arbitrary table myOldTable which is sufficiently long you could use the following trick:

set @counter = 0;
select (@counter := @counter+1), @counter*@counter from myOldTable limit 1000;

Answer 3

There's a trick with limited use-cases that is "loop-like".

I wanted to create a large (1~2 million) row table of random integers for a test:

INSERT INTO test_table (num) VALUES(ROUND(RAND() * 1E6));

-- calling this will insert once for every row in test_table
INSERT INTO test_table (num)
SELECT ROUND(RAND() * 1E6)
FROM test_table;

So I quickly just kept doubling the number of rows until I had what I needed.

Answer 4

If it is that you only want to block the current thread then use select sleep(seconds); otherwise you can use a stored procedure (if there's something you want to loop over) or a UDF (user defined function).