Question

This is a follow up to this question.

Here is my schema

CREATE TABLE A(      id serial NOT NULL,      date timestamp without time zone,      type text,      sub_type text,      filename text,      filepath text,      filesize integer,      lock_status int  ); 

In this database, a user can update the type,sub-type,filename,filepath,filesize as long as ‘lock_status’ is not set.

So, in the web page code (php) I can check the lock_status before updating the item.

However, there could be a case where another user has updated the lock status in the time between the first user’s check & update.

So, is there a way in SQL to check the lock status before the row gets updated?

• webpage code is in php
• database is PostgreSQL

edit added type,sub-type to the editable field list above

Answer 1

Sure, use UPDATE ... WHERE lock_status = 0. Alternatively, you could try using stored procedures.