Data integrity refers to the state in which all of the data values stored in the database are correct. If incorrect data values have been stored in a database, the database is said to have lost data integrity. This chapter provides an overview of the various methods that you can use to maintain data integrity and gives you a description of the types of data integrity that you will find in a SQL Server database. The chapter then provides detailed information about the various types of integrity constraints that you can use to enforce data integrity and describes how to implement them in a database.