In a table in our Oracle installation we have a table with an index on two of the columns (X and Y). If I do a query on the table with a where clause only touching column X, will Oracle be able to use the index?
For example:
Table Y: Col_A, Col_B, Col_C,
Index exists on (Col_A, Col_B)
SELECT * FROM Table_Y WHERE Col_A = 'STACKOVERFLOW';
Will the index be used, or will a table scan be done?