Oracle automatically creates an index for each UNIQUE or PRIMARY KEY declaration. For example, if you create a table foo as follows: create table foo (a int primary key, b varchar(20) unique);Oracle will automatically create one index on foo.a and another on foo.b. Note that you cannot drop indexes for UNIQUE and PRIMARY KEY attributes. These indexes are dropped automatically when you drop the table or the key constraints (see the section on Constraints).To find out what indexes you have, use select index_name from user_indexes;
b varchar(20) unique);Oracle will automatically create one index on foo.a and another on foo.b. Note that you cannot drop indexes for UNIQUE and PRIMARY KEY attributes. These indexes are dropped automatically when you drop the table or the key constraints (see the section on Constraints).To find out what indexes you have, use select index_name from user_indexes;