SQL Optimizer for DB2 ZOS 5.6.1 - User Guide

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

Classification

SQL Information	Description
SQL name	Name of the SQL statement.
Classification	Statement type as classified by SQL Optimizer. Types include Simple, Complex, or Problematic.
Classification Rules Detail	Description
Details	Applicable SQL Classification Rules. Rules used for the classification process are set in the SQL Classification Options menu.
Note:SQL Classification information only displays for the original SQL statement.

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.

View Optimization Details

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

To view optimization details

1. Select the SQL Details tab in the main window.
2. In the Alternatives pane, click .

3. Select the SQL Information tab in the Optimize SQL window. Review the following for additional information:

   Optimization Details	Description
   Intelligence level	Intelligence level used for optimization. This option is set on the Optimizer Intelligence options page. Intelligence Options
   Semantically equivalent SQL statements	Number of semantically equivalent SQL statements generated by SQL Optimizer.
   Alternative execution plans produced	Number of alternative execution plans produced for the original SQL statement.
   SQL statements eliminated due to identical execution plans	Number of statement alternatives eliminated with the same execution plan as the original SQL statement. Note: SQL statements with the same execution plan produce the same run time because the database executes these statements in the same way. Therefore, SQL Optimizer eliminates alternatives with equivalent execution plans.
   Optimization Time Details	Description
   Optimization started at	Time optimization started.
   Optimization finished at	Time optimization finished.
   Total optimization time	Total time to complete optimization.
   Average optimization time	Average time to generate each statement alternative.
   Notes: This information is only available after you generate SQL alternatives. Optimization details only display for the original SQL statement.