If conditions are specified for multiple-column indexed columns, two cases can be distinguished.
- Equality conditions:
Several equality conditions are specified for several multiple-column indexed columns which form a complete named index. The rows with keys that are contained in the corresponding index list of the named index are accessed.
- Equality conditions or conditions of ranges of values:
Several equality conditions or conditions of ranges of values combined by AND are specified for several multiple-column indexed columns.
Let a named index be formed by several columns (number n). If there is an equality or range condition for the first k (k<=n) columns of the index (a condition containing '<' or '>' may only be specified for the k-th column), only the rows with keys contained in the index lists of the specified range of values are accessed.
Examples:
The complete index list of the named index 'ind' with the values 'Düsseldorf', '40223', and 10000 is processed.
The index lists including the values 'Düsseldorf', '40221', (binary zeros) and 'Düsseldorf', '40238', (binary ones) are processed.
For both strategies, there are enquiries in case of which accessing the rows is not necessary, because all the required values are contained in the index list(s).