Selecting Expressions That Use Arithmetic Operators

You can combine numeric expressions with arithmetic operators to make complex expressions. You cannot combine expressions that contain aggregate functions with column expressions. These examples show expressions that use arithmetic operators within a select list in the Projection clause:

SELECT stock_num, quantity*total_price FROM customer;
SELECT price*2 doubleprice FROM items;
SELECT count(*)+2 FROM customer; 
SELECT count(*)+LENGTH('ab') FROM customer;