Mysql procedure increment variable

Question

I'm trying to get rank of user in the table with stored time.

RAW SQL query is working fine but I can't make it work as procedure.

SET @rownum := 0;
SELECT rank, user_id, best_time
FROM (
  SELECT @rownum := @rownum +1 AS rank,id, best_time, user_id
  FROM user_round WHERE round_id=1 ORDER BY best_time ASC
) AS result WHERE user_id = 1

My try to procedure:

BEGIN
 DECLARE variable INT DEFAULT 0;
 SELECT rank,best_time, user_id
 FROM (
  SELECT SET variable=variable+1 AS rank, best_time, user_id
  FROM database.user_round WHERE round_id=1 ORDER BY best_time ASC
 ) AS result WHERE user_id = 1;
END

Try removing `SET` from `SELECT SET variable=variable+1` – Aziz Shaikh Dec 03 '13 at 14:21 — Aziz Shaikh, Dec 03 '13 at 14:21
If i remove set I can save procedure but rank is always 0 – zajca Dec 03 '13 at 14:32 — zajca, Dec 03 '13 at 14:32

score 3 · Accepted Answer · answered Dec 03 '13 at 14:42

3

You need to continue using a 9.4. User-Defined Variables, not a 13.6.4.1. Local Variable DECLARE Syntax:

BEGIN
    -- DECLARE variable INT DEFAULT 0;
    SELECT rank, best_time, user_id
    FROM (
        -- SELECT SET variable = variable + 1 AS rank, best_time, user_id
        SELECT @variable := @variable + 1 AS rank, best_time, user_id
        FROM database.user_round, (SELECT @variable := 0) init
        WHERE round_id = 1
        ORDER BY best_time ASC
    ) AS result
    WHERE user_id = 1;
END

answered Dec 03 '13 at 14:42

wchiquito

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1

In this case you may have to watch out for this: `The difference between a procedure variable and a session variable is that procedure variable is reinitialized to NULL each time the procedure is called, while the session variable is not` as mentioned at: http://stackoverflow.com/a/1010042/ – Aziz Shaikh Dec 03 '13 at 14:55
@AzizShaikh: That's right, so it initializes the variable `@variable` in each execution of the stored procedure. See `(SELECT @variable := 0) init` – wchiquito Dec 03 '13 at 15:43
why should we stick to user variables, since they would fail the query if the stored procedure is called simultaneously from two or more threads? – Martin Asenov Jun 27 '14 at 21:05

Mysql procedure increment variable

1 Answers1