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

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

The database system chooses this search strategy in particular if the first key column was specified with an IN condition.

With this search strategy, the database system processes the individual values of the IN condition as an equality condition. In doing so the database system accesses the relevant table rows directly. The database system creates a intermediate result amount.

If the values of 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. In this case, the range condition is displayed in the execution plan.