Question

I am considering using triggers within my database to keep track of changes of bookings. Each time a booking is added I add a point to in a table that keeps a score in ‘tenure’.

When I run this command I am able to change the id before adding the trigger.

UPDATE bookit SET prov_id = 32 where book_id=2;

after adding the following trigger I get cannot update prov_id and get this error

1054 – Unknown column ‘bookit.prov_id’ in ‘where clause’

Trigger:

  delimiter //

 CREATE TRIGGER update_tenure_it BEFORE
 
 UPDATE ON bookit FOR EACH ROW

 BEGIN


 if(new.prov_id<>old.prov_id) THEN

 UPDATE provider_score set tenure=(tenure+1) where bookit.prov_id=provider_id;

 END IF;

 END;

 //

Do you know what I am doing wrong and where the issue comes from? Should I even consider using triggers for such operation or just code it in PHP? Thanks!

Answer 1

In triggers, you don’t have access directly to the table via TABLENAME.FIELD; instead, update triggers give you old.* and new.* as aliases of the row before and after the update fires, respectively. In this case, the following should work:

 delimiter //

 CREATE TRIGGER update_tenure_it BEFORE

 UPDATE ON bookit FOR EACH ROW

 BEGIN


 if(new.prov_id<>old.prov_id) THEN

 UPDATE provider_score set tenure=(tenure+1) where new.prov_id=provider_id;

 END IF;

 END;

 //