Sams Teach Yourself Microsoft

Lesson 11. Summarizing Data

In this lesson, you will learn what the SQL aggregate functions are and how to use them to summarize table data.

Using Aggregate Functions

It is often necessary to summarize data without actually retrieving it all, and SQL Server provides special functions for this purpose. Using these functions, T-SQL queries are often used to retrieve data for analysis and reporting purposes. Here are some examples of this type of retrieval:

• Determining the number of rows in a table (or the number of rows that meet some condition or contain a specific value)

• Obtaining the sum of a group of rows in a table

• Finding the highest, lowest, and average values in a table column (either for all rows ...