使用MariaDB / MySQL持续获得1064

Question

I'm struggling to get the below trigger to compile with my database. Right now its MariaDB v5.5.56. I have tried this syntax in online validators and here are the results:

SQLFiddle:

  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 '' at line 4

https://www.eversql.com/sql-syntax-check-validator/

 Great work, the query's syntax is valid!

https://rextester.com/l/mysql_online_compiler

 Compiles with no errors

In my environment I get:

 Error Code: 1064. 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 '' at line 4.

My error seems to match the SQLFiddle error...but its odd the other parsers worked just fine. Maybe there is something wrong with my syntax based on my DB version?

Here is what I am trying to execute:

 CREATE TRIGGER insert_pad
 BEFORE INSERT on vehicles FOR EACH ROW
 BEGIN
 DECLARE done INT DEFAULT FALSE;
 DECLARE localid CHAR(17);
 DECLARE veh_mod CHAR(17);
 DECLARE cur1 CURSOR FOR select id, RPAD(vin, 17,'Q') from   vehicles where length(rtrim(vin)) < 17;
 DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

 OPEN cur1;

 read_loop: LOOP
 FETCH cur1 INTO localid, veh_mod;

 IF done THEN
  LEAVE read_loop;
 END IF;
 UPDATE vehicles SET vin = veh_mod WHERE id = localid;


 END LOOP;

 CLOSE cur1;

 END;

If anyone has any thoughts I'd love to hear them! Thanks again!

Answer 1

I'm not seeing a change to the delimiter. Without that, the semicolon on line 4 is going to terminate the statement, and that's going to throw an error.

The DELIMITER statement changes the statement delimiter. We want to change to that to some string that doesn't appear in the statement we want to execute. In this example, we changing the delimiter to two dollar signs, and then changing it back to the default semicolon.

DELIMITER $$

CREATE TRIGGER insert_pad
BEFORE INSERT on vehicles FOR EACH ROW
BEGIN
  DECLARE done INT DEFAULT FALSE;
  DECLARE localid CHAR(17);
  ...
END$$

DELIMITER ;

---

Another thought: I don't think a trigger is allowed to issue DML (insert/update/delete) against a table that is referenced in the statement that causes the trigger to be fired.

But in a BEFORE INSERT trigger, we are allowed to reference and modify values of columns of the row that is about to be inserted. We use the special qualifier NEW. to reference columns in the row being inserted. For example:

 DELIMITER $$

 CREATE TRIGGER insert_pad
 BEFORE INSERT ON vehicles FOR EACH ROW
 BEGIN
   -- if vin less than 17 characters, pad with Q  
   IF( CHAR_LENGTH(TRIM( NEW.vin )) < 17 ) THEN
     SET NEW.vin = RPAD(TRIM( NEW.vin ), 17,'Q');
   END IF;
 END$$

 DELIMITER ;