RANGE CONDITION FOR INDEX 
RANGE CONDITION FOR INDEX is a search strategy of the SQL optimizer.
When Can the System Use This Strategy?
The database system accesses the table rows directly using the inventory lists that lie within the specified range. It therefore searches only part of the index and reads this part sequentially.
How Does the System Access the Data?
The database system can use this search strategy if one of the following conditions is met:
For the first k columns of an index, the search condition contains equality conditions (
1 ≤ k < n, n = number of index columns).The first index column was specified with a range condition.
The values of an IN condition are very close together.