O'Reilly logo

SQL Queries for Mere Mortals: A Hands-On Guide to Data Manipulation in SQL, Second Edition by Michael J. Hernandez, John L. Viescas

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

That “Nothing” Value: Null

As you know, a table consists of columns and rows. Each column represents a characteristic of the subject of the table, and each row represents a unique instance of the table’s subject. You can also think of a row as one complete set of column values—each row contains exactly one value from each column in the table. Figure 5-12 shows an example of a typical table.

Figure 5-12. A typical Customers table

So far we’ve shown how to retrieve information from the data in a table with a SELECT statement and how to manipulate that data by using value expressions. All of this works just fine because we’ve ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required