SQL UNION

The purpose of the SQL UNION query is to combine the results of two queries together while removing duplicates. In other words, when using UNION, only unique values are returned (similar to SELECT DISTINCT).

Syntax

The syntax of UNION in SQL is as follows:

The columns selected in [SQL Statement 1] and [SQL Statement 2] need to be of the same data type for UNION to work.

Example

We use the following tables for our example.

Table Store_Information

Table Internet_Sales

To find all the dates where there is a sales transaction, we use the following SQL statement:

Result:

Please note that if we type "SELECT DISTINCT Txn_Date" for either or both of the SQL statement, we will get the same result set.