SQL Query - Using Order By in UNION

Question

How can one programmatically sort a union query when pulling data from two tables? For example,

SELECT table1.field1 FROM table1 ORDER BY table1.field1
UNION
SELECT table2.field1 FROM table2 ORDER BY table2.field1

Throws an exception

Note: this is being attempted on MS Access Jet database engine

Answer 1

I think this does a good job of explaining.

The following is a UNION query that uses an ORDER BY clause:

select supplier_id, supplier_name
from suppliers
where supplier_id > 2000
UNION
select company_id, company_name
from companies
where company_id > 1000
ORDER BY 2;

Since the column names are different between the two "select" statements, it is more advantageous to reference the columns in the ORDER BY clause by their position in the result set.

In this example, we've sorted the results by supplier_name / company_name in ascending order, as denoted by the "ORDER BY 2".

The supplier_name / company_name fields are in position #2 in the result set.

Taken from here: http://www.techonthenet.com/sql/union.php

Answer 2

For Sql Server 2014/2012/Others(Not Checked) :

SELECT * FROM 
(
  SELECT table1.field1 FROM table1 ORDER BY table1.field1
) 
as DUMMY_ALIAS1

UNION ALL

SELECT * FROM
( 
  SELECT table2.field1 FROM table2 ORDER BY table2.field1
) 
as DUMMY_ALIAS2

Answer 3

Using a concrete example:

SELECT name FROM Folders ORDER BY name
UNION
SELECT name FROM Files ORDER BY name

Files:

name
=============================
RTS.exe
thiny1.etl
thing2.elt
f.txt
tcpdump_trial_license (1).zip

Folders:

name
============================
Contacts
Desktop
Downloads
Links
Favorites
My Documents

Desired Output: (results of first select first, i.e. folders first)

Contacts
Desktop
Downloads
Favorites
Links
My Documents
f.txt
RTMS.exe
tcpdump_trial_license (1).zip
thiny1.etl
thing2.elt

SQL to achieve the desired results:

SELECT name 
FROM (
    SELECT 1 AS rank, name FROM Folders
    UNION 
    SELECT 2 AS rank, name FROM Files) dt
ORDER BY rank, name

Answer 4

Browsing this comment section I came accross two different patterns answering the question. Sadly for SQL 2012, the second pattern doesn't work, so here's my "work around"

---

Order By on a Common Column

This is the easiest case you can encounter. Like many user pointed out, all you really need to do is add an Order By at the end of the query

SELECT a FROM table1
UNION
SELECT a FROM table2
ORDER BY field1

or

SELECT a FROM table1 ORDER BY field1
UNION
SELECT a FROM table2 ORDER BY field1

---

Order By on Different Columns

Here's where it actually gets tricky. Using SQL 2012, I tried the top post and it doesn't work.

SELECT * FROM 
(
  SELECT table1.field1 FROM table1 ORDER BY table1.field1
) DUMMY_ALIAS1

UNION ALL

SELECT * FROM
( 
  SELECT table2.field1 FROM table2 ORDER BY table2.field1
) DUMMY_ALIAS2

Following the recommandation in the comment I tried this

SELECT * FROM 
(
  SELECT TOP 100 PERCENT table1.field1 FROM table1 ORDER BY table1.field1
) DUMMY_ALIAS1

UNION ALL

SELECT * FROM
( 
  SELECT TOP 100 PERCENT table2.field1 FROM table2 ORDER BY table2.field1
) DUMMY_ALIAS2

This code did compile but the DUMMY_ALIAS1 and DUMMY_ALIAS2 override the Order By established in the Select statement which makes this unusable.

The only solution that I could think of, that worked for me was not using a union and instead making the queries run individually and then dealing with them. So basically, not using a Union when you want to Order By

Answer 5

(SELECT FIELD1 AS NEWFIELD FROM TABLE1 ORDER BY FIELD1)
UNION
(SELECT FIELD2 FROM TABLE2 ORDER BY FIELD2)
UNION
(SELECT FIELD3 FROM TABLE3 ORDER BY FIELD3) ORDER BY NEWFIELD

Try this. It worked for me.

Answer 6

If necessary to keep the inner sorting:

SELECT 1 as type, field1 FROM table1 
UNION 
SELECT 2 as type, field1 FROM table2 
ORDER BY type, field1

Answer 7

SELECT field1 FROM table1
UNION
SELECT field1 FROM table2
ORDER BY field1

Answer 8

(SELECT table1.field1 FROM table1 
UNION
SELECT table2.field1 FROM table2) ORDER BY field1 

Work? Remember think sets. Get the set you want using a union and then perform your operations on it.

Answer 9

Sometimes you need to have the ORDER BY in each of the sections that need to be combined with UNION.

In this case

SELECT * FROM 
(
  SELECT table1.field1 FROM table1 ORDER BY table1.field1
) DUMMY_ALIAS1

UNION ALL

SELECT * FROM
( 
  SELECT table2.field1 FROM table2 ORDER BY table2.field1
) DUMMY_ALIAS2

Answer 10

By using order separately each subset gets order, but not the whole set, which is what you would want uniting two tables.

You should use something like this to have one ordered set:

SELECT TOP (100) PERCENT field1, field2, field3, field4, field5 FROM 
(SELECT table1.field1, table1.field2, table1.field3, table1.field4, table1.field5 FROM table1
UNION ALL 
SELECT table2.field1, table2.field2, table2.field3, table2.field4, table2.field5 FROM  table2) 
AS unitedTables ORDER BY field5 DESC

Answer 11

This is the stupidest thing I've ever seen, but it works, and you can't argue with results.

SELECT *
FROM (
    SELECT table1.field1 FROM table1 ORDER BY table1.field1
    UNION
    SELECT table2.field1 FROM table2 ORDER BY table2.field1
) derivedTable

The interior of the derived table will not execute on its own, but as a derived table works perfectly fine. I've tried this on SS 2000, SS 2005, SS 2008 R2, and all three work.

Answer 12

This is how it is done

select * from 
    (select top 100 percent pointx, pointy from point
     where pointtype = 1
     order by pointy) A
union all
select * from 
    (select top 100 percent pointx, pointy from point
     where pointtype = 2
     order by pointy desc) B

Answer 13

SELECT field1
FROM ( SELECT field1 FROM table1
       UNION
       SELECT field1 FROM table2
     ) AS TBL
ORDER BY TBL.field1

(use ALIAS)

Answer 14

SELECT table1Column1 as col1,table1Column2 as col2
    FROM table1
UNION
(    SELECT table2Column1 as col1, table1Column2 as col2
         FROM table2
)
ORDER BY col1 ASC

Answer 15

Here's an example from Northwind 2007:

SELECT [Product ID], [Order Date], [Company Name], [Transaction], [Quantity]
FROM [Product Orders]
UNION SELECT [Product ID], [Creation Date], [Company Name], [Transaction], [Quantity]
FROM [Product Purchases]
ORDER BY [Order Date] DESC;

The ORDER BY clause just needs to be the last statement, after you've done all your unioning. You can union several sets together, then put an ORDER BY clause after the last set.

Answer 16

The second table cannot include the table name in the ORDER BY clause.

So...

SELECT table1.field1 FROM table1 ORDER BY table1.field1
UNION
SELECT table2.field1 FROM table2 ORDER BY field1

Does not throw an exception