Mariadb – Unexpected results from MariaDB IF EXISTS … THEN

existsmariadbstored-procedures

I am having unexpected results from MariaDB IF EXISTS… in a stored procedure. I created a minimal example to demonstrate the issue:

    PROCEDURE testdb.testSearchResults(IN pParam1 INT, IN pParam2 CHAR(2))
BEGIN

  IF EXISTS(SELECT COUNT(*) FROM test WHERE intval = pParam1 AND text = pParam2) THEN
    SELECT 'Found' AS result;
  ELSE
    SELECT 'Not Found' AS result;
  END IF;

END

No matter what the contents of the file "test" or the parameters I give to the call, this procedure always returns "Found".

Am I doing something wrong?

Thanks.

Best Answer

SELECT COUNT(*) always returns at least one record (maybe with zero). So IF EXISTS is always true.

You may:

  • Replace SELECT COUNT(*) ... with SELECT 1 ...

  • Replace IF EXISTS(SELECT ... with IF 0 < (SELECT ...

I think that 1st variant is more fast. It only checks does at least one record exists, and so it must stop searching after first record found, whereas 2nd query must obtain all matched records, count them, and then compare the result with zero.

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