The SQL UNION ALL Operator
The UNION ALL operator is used to combine the result-set of two or more SELECT statements.
The UNION ALL operator includes all rows from each statement, including any duplicates .
Requirements for UNION ALL
- Every SELECT statement within UNION ALL must have the same number of columns
- The columns must also have similar data types
- The columns in every SELECT statement must also be in the same order
UNION ALL Syntax
SELECT
column_name(s)
FROM
table1
UNION ALL SELECT
column_name(s)
FROM
table2
;Note
The column names in the result-set are usually equal to the column names in the first SELECT statement.
Demo Database
Below is a selection from the "Customers" table:
| CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
|---|---|---|---|---|---|---|
| 1 | Alfreds Futterkiste | Maria Anders | Obere Str. 57 | Berlin | 12209 | Germany |
| 2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 05021 | Mexico |
| 3 | Antonio Moreno TaquerÃa | Antonio Moreno | Mataderos 2312 | México D.F. | 05023 | Mexico |
And a selection from the "Suppliers" table:
| SupplierID | SupplierName | ContactName | Address | City | PostalCode | Country |
|---|---|---|---|---|---|---|
| 1 | Exotic Liquid | Charlotte Cooper | 49 Gilbert St. | London | EC1 4SD | UK |
| 2 | New Orleans Cajun Delights | Shelley Burke | P.O. Box 78934 | New Orleans | 70117 | USA |
| 3 | Grandma Kelly's Homestead | Regina Murphy | 707 Oxford Rd. | Ann Arbor | 48104 | USA |
SQL UNION ALL Example
The following SQL returns all the countries (also duplicate values) from both the "Customers" and the "Suppliers" table:
Example
SELECT Country FROM Customers
UNION ALL
SELECT Country FROM Suppliers
ORDER BY Country;SQL UNION ALL With WHERE
Here we add a WHERE clause to return all the German cities from both the "Customers" and the "Suppliers" table:
Example
SELECT City, Country FROM Customers
WHERE Country='Germany'
UNION ALL
SELECT City, Country FROM Suppliers
WHERE Country='Germany'
ORDER BY City;