SQL Optimizer for DB2 ZOS 5.5.1 - User Guide

Create User Defined Alternatives

In addition to using SQL Optimizer to generate alternative statements, you can create user defined alternatives. You can create user defined alternatives using SQL text from your original SQL statement or from SQL text of an alternative SQL Optimizer generated.

Note: This topic focuses on information that may be unfamiliar to you. It does not include all step and field descriptions.

To create a user defined alterative

1. Select the SQL Details tab in the main window.

2. Enter the SQL statement in the in the Alternative Details pane.

3. Click .

4. Edit the statement in the SQL Text pane to create a user defined alternative.

   Note: To create a user defined alternative using SQL text of an alternative SQL Optimizer generated, right-click an alternative and select User Alternative.

Caution: SQL Optimizer does not check that user defined alternatives are semantically equivalent to your original SQL statement. Review the execution statistics for user defined alternatives to compare the results with your original statement. See View Execution Statistics for more information.

Related Topics

Compare SQL Statements

Test Run SQL Alternatives

Set Bind Variables

You need to define the values of SQL statement variables before you optimize the statement. The Set Bind Variables window displays automatically when you use SQL Optimizer for a statement with variables.

Troubleshooting: If the Set Bind Variables window displays when you optimize a statement without variables, make sure you spelled the column and table names correctly, you selected the correct database or user, and you selected a table or column that exists in the database.

Note: This topic focuses on information that may be unfamiliar to you. It does not include all step and field descriptions.

To set a bind variable

1. Select the SQL Details tab in the main window.

2. Enter a SQL statement with a bind variable.

   Note: SQL Optimizer currently supports the following bind variables data type:

   • CHAR

   • NUMERIC
   • DECIMAL
   • INTEGER
   • SMALLINT
   • FLOAT
   • REAL
   • DOUBLE
   • DATETIME
   • VARCHAR
   • TYPE_DATE
   • TYPE_TIME
   • TYPE_TIMESTAMP
   • GRAPHIC
   • VARGRAPHIC
   • LONGVARGRAPHIC
   • BLOB
   • CLOB
   • DBCLOB
   • DATALINK

3. Click .

4. Review the following for additional information:

   Bind Variables List	Description
   Datatype	Click and select the variable datatype.
   Null	Select the checkbox if the value for the variable is null.
   Variable Value	Enter a value for the variable.
   Browse Data	Description
   SELECT	Click and select column references for the variables. Note: SQL Optimizer selects the All Columns checkbox by default.
   FROM	Click and select table references for the variables. Tip: Click to browse to tables in a different database.
   WHERE	Enter a WHERE clause or click to select a previously entered clause.
   ORDER BY	Enter a ORDER BY clause or click to select a previously entered clause.

Related Topics

Optimize SQL Statements

Test Run SQL Alternatives

Review Alternatives

Use the Alternatives pane to review the SQL text and execution plan for the alternatives SQL Optimizer generates. You can also review the run-time statistics for your original SQL statement and the alternatives after you execute the statements.

Note: This topic focuses on information that may be unfamiliar to you. It does not include all step and field descriptions.

To review details for an alternative

1. Select the SQL Details tab in the main window.

2. Select an alternative in the Alternatives pane.

3. Review details for the alternative in the Alternative Details and Execution Plan panes.

Related Topics  

Optimize SQL Statements

Automatically Optimize SQL Statements

Alternative SQL Text

Alternative SQL Text

The text editor is used to display the SQL text of the selected alternative. When there’s only original alternative or the selected alternative is user defined, the SQL text can be edited. Otherwise, it’s read-only.