Chapter 4. Group Operations

Group operations are quite common in the day-to-day life of a SQL programmer. If we use SQL to access a database, it is quite common to expect questions like:

• What is the maximum salary in this department?

• How many managers are there in each department?

• What is the number of customers for each product?

• Can we print the monthly aggregate sales for each region?

We need group operations to answer these questions. Oracle provides a rich set of features to handle group operations. These features include aggregate functions, the GROUP BY clause, the HAVING clause, the GROUPING function, and the extensions to the GROUP BY clause—ROLLUP and CUBE.

This chapter deals with simple group operations involving the aggregate functions, the GROUP BY and HAVING clauses. Advanced group operations such as GROUPING, ROLLUP, and CUBE are discussed in Chapter 12.