Left join with condition

Question

Suppose I have these tables

create table bug (
    id int primary key, 
    name varchar(20)
)
create table blocking (
    pk int primary key,
    id int, 
          


        

Answer 1

Here's a demo: http://sqlfiddle.com/#!2/414e6/1

select
  bug.id,
  bug.name,
  blocking.name as blockingType
from
  bug
    left outer join blocking on
      bug.id = blocking.id AND
      blocking.name = 'qa bug'
order by
  bug.id

By adding the "blocking.name" clause under the left outer join, rather than to the where, you indicate that it should also be consider "outer", or optional. When part of the where clause, it is considered required (which is why the null values were being filtered out).

BTW - sqlfiddle.com is my site.