Q: In SQL what does 'Group By' do?
A: The GROUP BY statement is used in conjunction with the aggregate functions(avg, sum, etc) to group the result-set by one or more columns. Note that only the columns used by the GROUP BY statement can be used in the SELECT statement.
fred| 100
bob| 100
fred| 400
SELECT Customer,SUM(OrderPrice) FROM Orders
GROUP BY Customer
fred| 500
bob| 400
