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In this chapter, you learned about defaults and the five types of constraints that can be placed on a column or table, and you learned how to create and modify defaults and constraints by using T-SQL commands and Enterprise Manager. You also learned how to create and modify defaults and rules by using Default and Rule objects. Defaults provide a way to specify a default value for a column when a specific value has not been assigned. Constraints provide various ways to enforce data integrity in your database. Defaults and constraints are helpful tools when they are thoughtfully applied to your database tables. In Chapter 17, we'll look at how to use indexes in SQL Server, including clustered and nonclustered indexes. Indexes can greatly improve the efficiency of data access.