IN CONDITION FOR INDEX is a search strategy of the database system.

The database system can choose this search strategy in the following situation: For the first k-1 columns of an index, equality conditions were specified and an IN condition was defined for the kth index column (1 <= k < n, n is the number of index columns).

The database system chooses this search strategy in particular if the first index column is specified with an IN condition. With this search strategy, the database system processes the individual values of the IN condition as an equality condition. Using the inversion lists, the database system accesses the corresponding table rows directly. The database system creates a intermediate result amount.

If the values in the IN condition are close together, or if many values were specified, it may be more practical for the database system to use a range condition instead of an equality condition. Multiple IN conditions can be considered on one index. In doing so it should be noted that the database system processes the second IN condition with one range only.