--Indexes.
--speed up DML ops (select, update, delete) on table when indexed
--column(s) used in Where clause.
--inserts slowed.
CREATE INDEX japan_bigint_index ON japan(bigint);
CREATE INDEX japan_bigword_index ON japan(bigword);

--Primary Key and Unique columns automatically have index.

--is B*-Tree unless specify Bitmap (for low cardinality column)
CREATE BITMAP INDEX japan_grade_index ON japan(grade);


--what indexes you have
SELECT index_name,table_name,uniqueness FROM ind;

--indexes on a table
SELECT index_name,table_name,uniqueness FROM ind WHERE table_name='EMPLOYEES';