Question

In this trigger:

  CREATE TRIGGER `after_insert_normas_revision`
    AFTER INSERT ON `normas_revision` FOR EACH ROW
    BEGIN

      DECLARE VAR_P_RHID INT;
      DECLARE VAR_P_VERSION INT;

      SELECT MAX(a.`rhID`)
      INTO VAR_P_RHID
        FROM `revision_history` a
        WHERE a.nID = new.`nID`;


      IF VAR_P_RHID IS NULL THEN
        SET VAR_P_VERSION = 0;
      ELSE
        SELECT `version`
          INTO VAR_P_VERSION
          FROM `revision_history` a
          WHERE a.`rhID` = VAR_P_RHID;
      END IF;

      DECLARE VAR_NEW_VERSION INT;
      SET VAR_NEW_VERSION = VAR_P_VERSION + 1;


      INSERT INTO `revision_history`
        (`revID`, `nID`, `userID`, `timestamp`, 
         `prev_rhID`, `version`, `action`, `comment`)
      VALUES
        (new.`revID`, new.`nID`, new.`userID`, CURRENT_TIMESTAMP, VAR_P_RHID, VAR_NEW_VERSION, 'UPDATE', new.`_rev_comment`);

    END

I’m getting this error

Schema Creation Failed: You have an error in your SQL syntax; check
the manual that corresponds to your MySQL server version for the right
syntax to use near ‘DECLARE VAR_NEW_VERSION INT;
SET VAR_NEW_VERSION = VAR_P_VERSION + 1;
‘ at line 23:

If I remove

DECLARE VAR_NEW_VERSION INT; 
SET VAR_NEW_VERSION = VAR_P_VERSION + 1

or change local variables to session variables (prepending with @) then the code runs allright.

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Q. Why does this happen?

Answer 1

The problem is in the syntax. It is incorrect.

All declarations must be at the begining of BEGIND…END clause. User variables you can set wherever you want in your code.