Question

I am currently looking a way to have my database under version control. To achieve so, I wanted to have deterministic procedures that can only be run only once (with corresponding undo).

I have a problem building my first script which is riddled with small bugs.

Here are the 3 main parts :

Condition to execute query (if field doesn’t exists)

SELECT *
FROM information_schema.COLUMNS
WHERE TABLE_SCHEMA = 'my_database'
  AND TABLE_NAME = 'my_table'
  AND COLUMN_NAME = 'full_name'

The table alteration:

ALTER TABLE
  my_table
  ADD full_name VARCHAR(255) NOT NULL;

And finally the data migration

UPDATE candidat dest JOIN candidat src ON dest.id = src.id
      SET dest.full_name = CONCAT(src.first_name, ' ', IF(src.middle_name='', '', CONCAT(src.middle_name, ' ')), src.last_name);

I’am trying to make this work in this form:

DELIMITER $$
DROP PROCEDURE IF EXISTS migration_001;

CREATE PROCEDURE migration_001()

BEGIN
  IF NOT EXISTS (
    SELECT *
    FROM information_schema.COLUMNS
    WHERE TABLE_SCHEMA = 'my_database'
      AND TABLE_NAME = 'my_table'
      AND COLUMN_NAME = 'full_name') 
   THEN

     ALTER TABLE
      my_table
      ADD full_name VARCHAR(255) NOT NULL;

    UPDATE candidat dest JOIN candidat src ON dest.id = src.id
          SET dest.full_name = CONCAT(src.first_name, ' ', IF(src.middle_name='', '', CONCAT(src.middle_name, ' ')), src.last_name);
  END IF
END;
$$

Current error I am getting:

1064 : ...  right syntax to use near 'CREATE PROCEDURE migration_001() BEGIN IF NOT EXISTS ( SELECT * ' at line 3

Can anyone point me in the right direction for solving this?

BTW I am using 5.5.16-log - MySQL Community Server.

Answer 1

Change the order of

DELIMITER $$

and

DROP PROCEDURE IF EXISTS migration_001;

Currently you are using the wrong delimiter to drop the procedure.