Avoiding Calculations on Indexed Columns -Oracle SQL Performance Tuning Tips -atz help

Avoiding Calculations on Indexed Columns -Oracle SQL Performance Tuning Tips -atz help

•The optimizer does not use an index if the indexed column is a part of a function (in the WHERE clause). In general, avoid doing calculations on indexed columns, apply function and concatenating on an indexed columns.

 

  Select * from

  Account

  Where substr(ac_acct_no,1,1) = ‘1’

 Instead use -

   Select * from

  Account

  Where ac_acct_no like ‘1%’

 Note : The SQL functions MIN and MAX are exceptions to this rule and will utilize all available indexes.

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