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SQL Optimizer for DB2 LUW 4.4.1 - Release Notes

Execution Result Tab

The Execution Result tab in the SQL Optimizer window compares the data returned by the original SQL with the data returned by any one of the SQL alternatives.

To compare all rows of data between the original SQL and an SQL alternative

  1. Select Unlimited for Max rows to compare.
  2. From the SQL list, select the SQL alternative that you want to compare with the original SQL.
  3. Click .

To compare a limited number of rows between the original SQL and an alternative

  1. Enter the number of rows in Max rows to compare.
  2. From the SQL list, select the SQL alternative that you want to compare with the original SQL.
  3. Click .

Comparison Grid

The grid in the top pane provides quick overview of returned-data differences. The numbers of returned columns and rows show whether the SQL alternative produces the same result as the original SQL statement. The displayed time shows how long it took to execute Batch Run or the Run Time, not the time it took to retrieve the data for the Execution Result tab.

Note: If the Data statistic shows that the returned data differs when you retrieve limited rows, do not assume that the alternative is returning wrong data. The difference can suggest that the alternative has returned data in an order different from the order returned by the original SQL. Two SQL statement are considered to be semantically equivalent if they retrieve the same data in any order (as long as the ORDER BY clause is not used in the SQL statement).

Comparison Functions

To refresh the data for the currently selected alternative

Click .

To clear all the data for original and all alternatives

Click .

To abort Compare SQL or Refresh SQL process

Click .

 

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