CREATE TABLE CUSTOMERS(
   ID   INT              NOT NULL,
   NAME VARCHAR (20)     NOT NULL,
   AGE  INT              NOT NULL,
   ADDRESS  CHAR (25) ,
   SALARY   DECIMAL (18, 2),       
   PRIMARY KEY (ID)
);

CREATE INDEX index_name
   ON table_name ( column1, column2.....);

CREATE INDEX idx_age
   ON CUSTOMERS ( AGE );

ALTER TABLE CUSTOMERS
   DROP INDEX idx_age;