[Update Oct ‘09 In response to a number of comments on this post regarding problems with this approach, I’ve added a new blog entry with more details. Check it out.]
Those with a SqlServer background will be familiar with the UPDATE .. FROM syntax.
For example (totally made up)
1: update employee_bonus
2: set bonus = 0
3: from employee_bonus b
4: inner join employees e on b.employee_id = e.employee_id
5: where e.bonus_eligible = 'N'
Those who transitioned from SqlServer to Oracle might find the absence of the UPDATE FROM a significant loss. The best Oracle alternative that I know of is as follows.
1: update (select bonus
2: from employee_bonus b
3: inner join employees e on b.employee_id = e.employee_id
4: where e.bonus_eligible = 'N') t
5: set t.bonus = 0
Actually, if you look at it, they are very similar.
In fact Oracle has quite a bit of power in the UPDATE. Check out this reference. The syntax in the statement above utilizes the subquery1 block in the diagram below.
Happy coding.
Tags: Oracle, SQL