SQL UNION ALL use UNION ALL instead of UNION for Better Performance

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Topic: SQL UNION ALL use UNION ALL instead of UNION for Better Performance (Read 153 times)

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SQL UNION ALL use UNION ALL instead of UNION for Better Performance

« on: December 28, 2011, 06:39:39 AM »

SQL UNION ALL use UNION ALL instead of UNION in WHERE clause for Better Performance

Use this query for better query performance:
Use UNION ALL if you don't worry for duplicate data.

Code: [Select]

select  field_1,field_2 from my_table1
UNION ALL
select  field_1,field_2 from my_table2

Instead of this query:

Code: [Select]

select  field_1,field_2 from my_table1
UNION
select  field_1,field_2 from my_table2

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SQL UNION ALL use UNION ALL instead of UNION for Better Performance

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Topic: SQL UNION ALL use UNION ALL instead of UNION for Better Performance (Read 153 times)

SQL UNION ALL use UNION ALL instead of UNION for Better Performance