EXPLAIN Statement: Columns O,D,T,M 

Column (Only Index)

'*'

This strategy uses only the specified single-column or multi-column index to process the command. The system does not access the basis table data. It is also necessary that only columns that are contained in the index structure are addressed as a result of selected columns (<select_column>) or in a WHERE clause, if one exists.

Column D (Distinct Optimization)

Column D only has an entry if column O contains the character ‘*’.

Column T (Temporary Index)

'*'

A temporary index is created internally, in which the keys of the hit lines determined through the corresponding index are stored in ascending order. The system accesses the basis table using this temporary index.

Column M (More Qualifications)

'*'

There are search conditions for index or key columns that cannot be used for the direct containment of the area for an index access (for example, in the case of a equality /IN condition, for the first and third columns of a multi-column index, only the first search condition of the search strategy is used for access). These search conditions flow into the corresponding index strategy. They are used to restrict accesses to the basis table.