The colmin and colmax column values hold the second-smallest and second-largest data values in the column, respectively. For example, if the values in an indexed column are 1, 2, 3, 4, and 5, the colmin value is 2 and the colmax value is 4. Storing the second-smallest and second-largest data values lets the database server make assumptions about the range of values in a given column and, in turn, further optimize search strategies.
The colmin and colmax columns contain values only if the column is indexed and you have run the UPDATE STATISTICS statement. If you store BYTE or TEXT data in the tblspace, the colmin value is -1.
The colmin and colmax columns are valid only for data types that fit into four bytes: SMALLFLOAT, SMALLINT, INTEGER, and the first four bytes of CHAR. The values for all other noninteger column types are the initial four bytes of the maximum or minimum value, which are treated as integers.
It is better to use UPDATE STATISTICS MEDIUM than to depend on colmin and colmax values. UPDATE STATISTICS MEDIUM gives better information and is valid for all data types.
Dynamic Server does not calculate colmin and colmax values for user-defined data types. These columns, however, have values for user-defined data types if a user-defined secondary access method supplies them.
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