EXPLAIN Statement: Columns O,D,T,M (SAP Library

EXPLAIN Statement: Columns O,D,T,M

Column O (Only Index)

'*'

This strategy uses only the specified index to process the command. The system does not access the basis table data. To do this, it is 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 ‘*’.

'C' (Complete Secondary Key)
All columns of an index (and only these) are specified as a result of selected columns (<select_column>), after the keyword DISTINCT (DISTINCT specification (distinct_spec)), in any order. The system accesses the values for each index column only once. The system does not create a results table (such as SELECT DISTINCT <all_columns_of_the_index> FROM ...).

'P' (Partial Secondary Key)
The first k (k < Total number of index columns) columns of an index are specified are specified in any order as a result of selected columns (<select_column>), after the key word DISTINCT. The system accesses the values for each index column only once. The system does not create a results table (such as SELECT DISTINCT <first_k_columns_of_the_index> FROM ...).

'K' (Primary Key)
All columns of an index, and the first k (k <= total number of columns in the key) columns of the key are specified in any order as a result of selected columns (<select_column>), after the keyword DISTINCT. The system accesses the values for the corresponding index and key columns only once. The system does not create a results table (such as SELECT DISTINCT <all_columns_of_the_index_+_first_k_columns_of_the_key> FROM ...).

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 an 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.