JavaScript Example:

create database kavi;
                use kavi;
                
                create table salesman(
                salesman_id int(10),
                name varchar(100),
                city varchar(100),
                commission varchar(10));
                
                create table customer(
                customer_id int(10),
                name varchar(100),
                city varchar(100),
                grade int(10));
                
                create table orders(
                orders_no int(10),
                purchase_amt int(10),
                customer_id int(10),
                salesman_id int(10));
                
                insert into salesman values(1000,'oviyaa','bangalore','25%');
                insert into salesman values(2000,'priya','bangalore','29%');
                insert into salesman values(3000,'kaviyaa','bangalore','35%');
                insert into salesman values(4000,'rose','bangalore','55%');
                
                insert into customer values(10,'vika','bangalore',1);
                insert into customer values(11,'maha','bangalore',3);
                insert into customer values(12,'varsha','bangalore',5);
                insert into customer values(13,'yuva','bangalore',8);
                
                insert into orders values(50,5000,10,1000);
                insert into orders values(60,6000,10,2000);
                insert into orders values(70,8000,13,9000);
                insert into orders values(80,9000,17,6000);
                
                select * from salesman;
                select * from customer;
                select * from orders;
                
                SELECT COUNT(DISTINCT CUSTOMER_ID)
                FROM CUSTOMER
                WHERE GRADE > (SELECT AVG(GRADE) FROM CUSTOMER WHERE CITY = 'BANGALORE');