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SQL Performance DOs and DON'Ts |
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Written by Anon.
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Sunday, 11 March 2007 |
DO | DON’T | | Select <fields> from <table>. | Select * from <table>. | | SELECT <fields> INTO TABLE <internal table> | SELECT <fields> INTO CORRESPONDING FIELDS OF TABLE <internal table> | | Select <field> from <table> Up To 1 Rows <structure>. | Select count(*) from <table>. | | Select <fields> from <table> into table <internal table>. Sort <internal table> By <sort fields>. | Select <fields> from <table> into table <internal table> order by <fields>. | | Select <fields> from <table> into table <internal table>. Sort <internal table>. Delete Adjacent Duplicates from <internal table>. | | | | Addition CLIENT SPECIFIED in SQL’s | | OPEN SQL. | Native SQL. | | Joins** | Nested Select / Logical Databases or Selects inside a loop. | | | SELECT SINGLE FOR UPDATE** | | IS NULL, IS NOT NULL, LIKE or NOT LIKE** | | | Select single** | | | | Group By or Having** or Aggregate Functions (AVG, MAX, MIN, SUM)** | | Subqueries** | | | Use ‘For All Entries’ technique as a second alternate to JOINs. | | | Use alternate index tables for data access | |
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