UNION [ALL]¶

The UNION set operation clause combines the result sets of two or more SELECT statements, removing duplicates.

The UNION ALL set operation clause combines the result sets of two or more SELECT statements, allowing duplicates.

Syntax¶

SELECT <column_name> [ ,... ]
FROM <table1>
UNION [ ALL ]
SELECT <column_name> [ ,... ]
FROM <table2>

Parameter	Description
`column_name`	The columns to retrieve
`table1`	The table from which to retrieve the data
`table2`	The table from which to retrieve the data
`ALL`	Allows the `UNION` to return duplicate rows in the result set

SELECT
  city
FROM
  customers
UNION ALL
SELECT
  city
FROM
  suppliers;

SELECT
  city
FROM
  customers
UNION ALL
SELECT
  city
FROM
  suppliers;