The sysstatistics table stores one or more rows for each indexed column on a user table. In addition, it can store statistics for unindexed columns.
The first row for each column stores basic statistics about the column, such as the density for joins and search arguments, the selectivity for some operators, and the number of steps stored in the histogram for the column. If the index has multiple columns, or if you specify multiple columns when you generate statistics for unindexed columns, there is a row for each prefix subset of columns.
For more information on prefix subsets, see “Column statistics”.
Additional rows store histogram data for the leading column. Histograms do not exist if indexes were created before any data was inserted into a table (run update statistics after inserting data to generate the histogram).
See “Histogram displays” for more information.
See the Adaptive Server Reference Manual for more information.