SQL Server: How to use UNION with two queries that BOTH have a WHERE clause?

Question

Given:

Two queries that require filtering:

select top 2 t1.ID, t1.ReceivedDate
  from Table t1
 where t1.Type = \'TYPE_1\'
 order by         


        

Answer 1

You should be able to alias them and use as subqueries (part of the reason your first effort was invalid was because the first select had two columns (ID and ReceivedDate) but your second only had one (ID) - also, Type is a reserved word in SQL Server, and can't be used as you had it as a column name):

declare @Tbl1 table(ID int, ReceivedDate datetime, ItemType Varchar(10))
declare @Tbl2 table(ID int, ReceivedDate datetime, ItemType Varchar(10))

insert into @Tbl1 values(1, '20010101', 'Type_1')
insert into @Tbl1 values(2, '20010102', 'Type_1')
insert into @Tbl1 values(3, '20010103', 'Type_3')

insert into @Tbl2 values(10, '20010101', 'Type_2')
insert into @Tbl2 values(20, '20010102', 'Type_3')
insert into @Tbl2 values(30, '20010103', 'Type_2')

SELECT a.ID, a.ReceivedDate FROM
 (select top 2 t1.ID, t1.ReceivedDate
  from @tbl1 t1
  where t1.ItemType = 'TYPE_1'
  order by ReceivedDate desc
 ) a
union
SELECT b.ID, b.ReceivedDate FROM
 (select top 2 t2.ID, t2.ReceivedDate
  from @tbl2 t2
  where t2.ItemType = 'TYPE_2'
  order by t2.ReceivedDate desc
 ) b