sql sort
Primary key 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 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, NAME) ); ALTER TABLE CUSTOMER ADD PRIMARY KEY (ID); ALTER TABLE CUSTOMERS ADD CONSTRAINT PK_CUSTID PRIMARY KEY ( ID , NAME ); ALTER TABLE CUSTOMERS DROP PRIMARY KEY ; foreign key CUSTOMERS table 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 ) ); ORDERS table CREATE TABLE ORDERS ( ID INT NOT NULL , DATE DATETIME , CUSTOMER_ID INT reference