An SQL statement can reference the same table multiple times; each reference is represented by a table node.
A table node is labeled with the name of the referenced table and is, by default, displayed as a rectangle. The correlation name, creator name, or cardinality of the table can also be displayed on the label. If the RUNSTATS utility has not collected statistics for the table, the table node is outlined in red. If the optimizer uses the default value for the table cardinality, the cardinality is marked as the default. The default cardinality value is stored in the catalog table SYSIBM.SYSTABLES as -1; however, the optimizer uses 10 000 as the default value.
If RUNSTATS has not collected statistics, the optimizer does not necessarily use the default values. If you manually update the values in SYSIBM.SYSTABLES, the optimizer uses these values and not the default values.
Attribute | Explanation | Default value |
---|---|---|
Rows | Total number of rows | 10 000 |
Pages | Total number of pages | 501 |
Compressed Row Percentage | Percentage of compressed rows | 0 |