SQL Set Operations

The SQL Set operations is used to combine the two or more sql statements.

Types of Set operations:

• Union
• Unionall
• Intersect
• Minus

Union Operation:

• The SQL Union operation is used to combine the result of two or more SQL SELECT queries.
• In the union operation, all the number of datatype and columns must be same in both the tables on which UNION operation is being applied. 
• The columns in every SELECT statement must also be in the same order
• The union operation eliminates the duplicate rows from its resultset.

 Syntax

 SELECT Column_name FROM table1 

UNION

 SELECT column_name FROM table2;

 Example

 SELECT * FROM First 

UNION

 SELECT * FROM Second;

Union all operation:

The UNION operator selects only distinct values by default. To allow duplicate values, use UNION ALL:

SELECT column_name(s) FROM table1
UNION ALL
SELECT column_name(s) FROM table2;

Intersect Operation

• It is used to combine two SELECT statements. 
• The Intersect operation returns the common rows from both the SELECT statements.
• In the Intersect operation, the number of datatype and columns must be the same.
• It has no duplicates and it arranges the data in ascending order by default.

Syntax

SELECT column_name FROM table1

INTERSECT

SELECT column_name FROM table2;

Example

SELECT * FROM First

INTERSECT

SELECT * FROM Second;

MINUSOperation

• It combines the result of two SELECT statements. 
• Minus operator is used to display the rows which are present in the first query but absent in the second query.
• It has no duplicates and data arranged in ascending order by default.

Syntax

SELECT column_name FROM table1

MINUS

SELECT column_name FROM table2;

Example

SELECT * FROM First

MINUS

SELECT * FROM Second