The usual output is based on statistics generated by the optimization process, as described in Database Statistics.

By default, optimizer statistics are shown for all tables and columns in the current database, but you can view statistics for specific table columns.

The following command lists statistics for the empno column of the emp table:

In Director or VDBA, use the Specify Tables and Specify Columns check boxes in the Display Statistics dialog.

To delete statistics, use the -zdl flag with the statdump command. Use the -r and -a flags to specify the tables and columns for which to delete statistics.

This command deletes statistics from the demodb database: columns empno and sex from the emp table and the empno column from the task table:

In Director, use the Display Statistics dialog, Options page.

In VDBA, enable the Delete Statistics from Syscat check box. Using this check box in conjunction with the Specify Tables and Specify Columns check boxes, you can specify the tables and columns for which to delete statistics.

For example, enable the Delete Statistics from Syscat check box, specify the empno and sex columns from the emp table and the empno column from the task table.

You can specify the precision with which floating point numbers are displayed in the statistics by enabling the Set Precision Level to check box and entering a value in the corresponding edit control to determine the number of decimal digits in the text format of the floating point numbers.

For example, assume a table, t_float, is defined with a column named c_float of type float, and that the following statements are used to insert values (all of which are approximately 1.0):

You can create statistics for this table using the optimization procedure described in Database Statistics.

With its default floating point precision, the standard output is show seven places after the decimal point. For greater precision, you can enable the Set Precision Level check box and enter a larger value.

For example, specifying a precision level of 14 generates output like the following, in which there is sufficient precision to maintain a visible difference in the values:

This can be useful when statistics are output to a text file or input from a text file. For more information, see Statistics in Text Files. When reading statistics from a text file, the optimization process assumes that all cell values are in ascending order. You can use the Set Precision Level option to preserve sufficient precision for floating point numbers.