Exercises Read the following description and then answer questions 1-5 at the end. The Check Constraint The check constraint enforces domain integrity. In other words, you can't invoice a nonexistent customer. When you place a primary-key constraint on a column, you're requiring each row in that column to have a unique value, which can't be NULL.
And you can't disable the checking of existing data because SQL Server can create the index only on data that contains no duplicate values. You can have only one primary-key constraint per table. Practice Questions: Constraints and Integrity," page 70, at the link to this article at http: The primary keys are identified below. You can remove a constraint from the table without affecting the table or the data, and you can temporarily disable certain constraints.
Constraints are a very important feature in a relational model. The invoices table might have several entries for one customer. Or it could be a many-to-one relationship. Answer to Define interrelation constraint and give one example of such a constraint. A foreign-key constraint doesn't automatically build an index.
Constraints and Integrity. Louisiana State University. In Figure 9. Key Terms business rules: Note the naming convention SQL Server uses: The one side is mandatory.
An identifying relationship will have a solid line where the PK contains the FK. Give an example other than one in this chapter.