RANGE CONDITION FOR KEY is a search strategy of the SQL optimizer.
The database system searches the specified range of the table sequentially. To restrict the range, the system sets a start and a stop key.
The database system uses this search strategy if one of the following conditions is met:
For the first k columns of the primary key, equality conditions were specified (1 ≤ k < n
, n = number of key columns). All other key columns were either not specified at all or were specified
with a range condition.
The first key column was specified with a range condition.
The values of an IN condition are very close together.