UNION or UNION ALL is one of famous clause can be used in SQL Server to join 2 or more query to be one result. But, the point is what is the differences between UNION and UNION ALL ?.
Please kindly execute below query:
[code language=”sql” title=”Sample UNION & UNION ALL”]
— sample UNION
SELECT ‘arif’, 1
UNION
SELECT ‘arif’, 2
— sample UNION ALL
SELECT ‘arif’, 1
UNION ALL
SELECT ‘arif’, 2
[/code]
The result both is same, but please kindly execute below query:
[code language=”sql” title=”Sample UNION & UNION ALL”]
— sample UNION
SELECT ‘arif’, 1
UNION
SELECT ‘arif’, 1
— sample UNION ALL
SELECT ‘arif’, 1
UNION ALL
SELECT ‘arif’, 1
[/code]
The result is different.
My conclusion is UNION can join 2 or more query with avoiding duplicate value whereas UNION ALL doesn’t. If you have better or deeper explanation, please kindly contact me.
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