UNION keyword

Overview

UNION is used to combine the results of two or more SELECT statements. To work properly:

• Each select statement should return the same number of column
• Each column should have the same type
• Columns should be in the same order

Syntax

• UNION will return distinct results.
• UNION ALL will return all results including duplicates.

Examples

Let's assume the following two tables listA

Description	ID
Red Pen	1
Blue Pen	2
Green Pen	3

listB

Description	ID
Pink Pen	1
Black Pen	2
Green Pen	3

liastA UNION listB

will return

Description	ID
Red Pen	1
Blue Pen	2
Green Pen	3
Pink Pen	1
Black Pen	2

liastA UNION ALL listB

will return

Description	ID
Red Pen	1
Blue Pen	2
Green Pen	3
Pink Pen	1
Black Pen	2
Green Pen	3