The following sample shows statistics for the city column in the authors table:
Statistics for column: "au_lname" Derived statistics from local partitions. Last update of column statistics: Apr 8 2008 9:29:07:706PM Range cell density: 0.0005507993510047 Total density: 0.0005507993510047 Range selectivity: default used (0.33) In between selectivity: default used (0.25) Unique range values: 0.0005215561314205 Unique total values: 0.0005215561314205 Average column width: 6.7988000000000000
Row label |
Information provided |
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Statistics for column |
Name of the column; if this block of information provides information about a prefix subset in a compound index or column list, the row label is “Statistics for column group.” |
Last update of column statistics |
Date the index was created, date that update statistics was last run, or date that optdiag was last used to change statistics. |
Statistics originated from upgrade of distribution page |
Statistics resulted from an upgrade from a distribution page from a version of Adaptive Server earlier than 11.9. This message is not printed if update statistics has been run on the table or index, or if the index has been dropped and re-created after an upgrade. If this message appears in optdiag output, run update statistics . |
Statistics loaded from optdiag |
optdiag was used to change sysstatistics information. create index commands print warning messages indicating that edited statistics are being overwritten. This row is not displayed if the statistics were generated by update statistics or create index. |
Range cell density |
Density for equality search arguments on the column. |
Total density |
Join density for the column. This value is used to estimate the number of rows that will be returned for a join on this column. |
Range selectivity |
Prints the default value of .33, unless the value has been updated using optdiag input mode. This is the value used for range queries if the search argument is not known. See “Range and in-between selectivity values” below. |
In between selectivity |
Prints the default value of .25, unless the value has been updated using optdiag input mode. This is the value used for range queries if the search argument is not known. See “Range and in-between selectivity values” below. |
Unique range values |
Number of unique values in a column, excluding the frequency cells. |
Unique total values |
Total number of unique values. |
Average column width |
Average of all column widths from the table. |