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You use the syntax for a multiple-field constraint whenever you use the reserved word CONSTRAINT outside a field-definition clause in an ALTER TABLE or CREATE TABLE statement.

Using CONSTRAINT you can designate a field as one of the following types of constraints: To prevent the automatic creation of indexes for foreign keys, the modifier NO INDEX can be used.

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However, consider temporarily disabling the integrity constraints of a table for the following performance reasons: In all three cases, temporarily disabling integrity constraints can improve the performance of the operation, especially in data warehouse configurations.

It is possible to enter data that violates a constraint while that constraint is disabled.

Hence, enabling without validating enables you to reduce the downtime typically associated with enabling a constraint.

statement that defines and disables an integrity constraint never fails because of rows in the table that violate the integrity constraint.

This form of foreign key definition should be used only in cases where the resulting index values would be frequently duplicated.

Where the values in a foreign key index are frequently duplicated, using an index can be less efficient than simply performing a table scan.

If a constraint is disabled, then data that does not conform can be allowed to enter the database.

Additionally, you can specify that existing data in the table must conform to the constraint ( To enforce the rules defined by integrity constraints, the constraints should always be enabled.

Maintaining this type of index, with rows inserted and deleted from the table, degrades performance and does not provide any benefit.

This example creates a new table called This Table with two text fields.

Close End Sub Sub Create Table X3() Dim dbs As Database ' Modify this line to include the path to Northwind ' on your computer.

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