Re: help with a simple query

May be something like:

select * from a
where a.col1 = val1

   or ( a.col1 is null

      and exists (select 1 from b
                  where b.col2 = a.col2
                    and b.col1 = val1) );

or

select * from a where a.col1 = val1
union all
select a.* from a, b

where a.col1 is null
  and b.col2 = a.col2
  and b.col1 = val1;

--
Have a nice day
Michel


<javadrink_at_my-deja.com> a écrit dans le message : 91m0jq$dl2$1_at_nnrp1.deja.com...


> I need to do a following query (using table a, b):

>

>

> select *

> from a

> where a.col1=val1  or if a.col1=null then b.col1=val1

>                       wherea.col2 = b.col2

>

> how to express the if part using SQL?  thanks a lot!

>

> (basically what I want to do is: selection based tableA column1, but if

> tableA column1 is null, join tableA with tableB using column2 and make

> sure tableB column 1 equal to the input value)

>

> Thanks!

>

>

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