What Is Union In SQL?
The UNION operator is used to combine the result-set of two or more data set .
- Each SELECT statement within UNION must have the same number of columns
- The columns must also have similar data types
- The columns in each SELECT statement must also be in the same order
Difference Between Union and Union ALL In SQL ?
/*Union
Removes Duplicate Rows,So it Apply expensive Distinct sort opertaion */
SELECT
1 AS
ID,'Anoop'
AS
Name
UNION
SELECT
1 AS
ID,'Anoop'
AS
Name
UNION
SELECT
2 AS
ID,'Manu'
AS
Name
/*Union
ALL Returs All Rows, So it is better to use unionAll instead of union*/
SELECT
1 AS
ID,'Anoop'
AS
Name
UNION
ALL
SELECT
1 AS
ID,'Anoop'
AS
Name
UNION
ALL
SELECT
2 AS
ID,'Manu'
AS
Name
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