Difference Between Union Unionall Except Intersect

• The SQL UNION ALL operator is used to combine the result sets of 2 or more SELECT statements.
• It does not remove duplicate rows between the various SELECT statements (all rows are returned).
• Each SELECT statement within the UNION ALL must have the same number of fields in the result sets with similar data types.

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Syntax

• The syntax for UNION ALL is as follows:

[SQL Statement 1]
UNION ALL
[SQL Statement 2];

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

Anatomy of a Union

SQL Union All Query

Example

• We use the following tables for our example.

Table Store_Information

Store_Name	Sales	Txn_Date
Los Angeles	1500	Jan-05-1999
San Diego	250	Jan-07-1999
Los Angeles	300	Jan-08-1999
Boston	700	Jan-08-1999

Table Internet_Sales

Txn_Date	Sales
Jan-07-1999	250
Jan-10-1999	535
Jan-11-1999	320
Jan-12-1999	750

• · To find out all the dates where there is a sales transaction at a store as well as all the dates where there is a sale over the internet, we use the following SQL statement:

SELECT Txn_Date FROM Store_Information
UNION ALL
SELECT Txn_Date FROM Internet_Sales;

Result:

Txn_Date
Jan-05-1999
Jan-07-1999
Jan-08-1999
Jan-08-1999
Jan-07-1999
Jan-10-1999
Jan-11-1999
Jan-12-1999

Union vs Union All

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