Question

I need to write a query.
have 3 tables, one main and two associated
for example :

main_table
id   name
--   -------------
1    example
2    example2

join_table1
id   main_table_id
--   -------------
 1     1

join_table2
id   main_table_id
--   -------------
1      2

if main_table_id contained in join_table1
I need to sort by join_table1.id, else if main_table_id contained in join_table2,

i need to sort by join_table2.id

any ideas how to make such query
main_table_id can be either in table join_table1 or join_table2
database – SQL Server

Answer 1

You should combine coalesce and left joins. Query will look like:

select ...
from main_table
left outer join join_table1 j1 on ...
left outer join join_table2 j2 on ...
order by coalesce( j1.id, j2.id )