Help need for Outer Join Query Mysterious Query...

Question

I have two table parent tablea and child tableb
Now
tableb has field by name table_id,keyword_name,keyword_value
tablea has field by name
table_id,table_name
I need a query which would retrieve union of this two set...(for table_name)
1)all table_name having keyword_name='abc' and value=12
2)all the table_name that does not have 'abc' as keyword in tableb.....
Please let me know how it can be done....

Answer 1

Ok then, try this.
select
    a.table_name
from
    tablea a, tableb b
where
    a.table_id = b.table_id
    and b.keyword_name = 'abc'
    and b.value = 12
union
select
    c.table_name
from
    tablea c
where
    not exists (select 1 from tableb d
                where d.table_id = c.table_id
                      and d.keyword_name = 'abc'
               ) ;To get a faster answer and avoid wrong guesses, I always find it helpful to show sample data and sample output when asking a SQL question. For example:
TableA -----------------
table_id    table_name
  1           AAA
  2           BBB
  3           CCC
  4           DDD
  5           EEE
TableB -----------------
table_id    keyword_name   value
    1             abc       12
    1             def       23
    2             abc       13
    4             def       12
    5             abc       13
    5             def       12
Desired output of query: -----------------
AAA
CCC
DDD