• Article

Foreign Key Relationships Dialog Box (Visual Database Tools)

Use this dialog box to create or modify relationships between tables in your database. In a foreign key relationship, FOREIGN KEY constraints work with PRIMARY KEY or UNIQUE constraints to enforce referential integrity among specified tables. For example, you can place a FOREIGN KEY constraint on the ProductID column in the Order_Details table to ensure that a value entered in that column matches an existing value in the ProductID column of the Products table.

Note

If the table is published for replication, you must make schema changes by using the ALTER TABLETransact-SQL statement or SQL Server Management Objects (SMO). When schema changes are made using the Table Designer or the Database Diagram Designer, it attempts to drop and re-create the table. You cannot drop published objects; therefore, the schema change will fail.

To access this dialog box, open the table definition for the table with the foreign key, right-click the table definition grid, and click Relationships.

Options

  • Selected Relationship
    Lists existing relationships. Select a relationship to show its properties in the grid to the right. If the list is empty, no relationships have been defined for the table.

  • Add
    Create a new relationship. The Tables and Columns Specifications must be set before the relationship will be valid.

  • Delete
    Delete the relationship selected in the Selected Relationships list. To cancel the addition of a relationship, use this button to remove the relationship.

  • General Category
    Expand to show Check Existing Data on Creation or RE-Enabling and Tables and Columns Specifications.

  • Check Existing Data on Creation or Re-Enabling
    Verify all existing data in the table before the constraint was created or re-enabled, against the constraint.

  • Tables and Columns Specifications Category
    Expand to show which columns from which tables act as the foreign key and primary (or unique) key in the relationship. To edit or define these values, click the ellipsis button (…) to the right of the property field.

  • Foreign Key Base Table
    Shows which table contains the column acting as a foreign key in the selected relationship.

  • Foreign Key Columns
    Shows which column acts as a foreign key in the selected relationship.

  • Primary/Unique Key Base Table
    Shows which table contains the column acting as a primary (or unique) key in the selected relationship.

  • Primary/Unique Key Columns
    Shows which column acts as a primary (or unique) key in the selected relationship.

  • Identity Category
    Expand to show the property fields for Name and Description.

  • Name
    Shows the name of the relationship. When a new relationship is created, it is given a default name based on the table in the active window in Table Designer. You can change the name at any time.

  • Description
    Describe the relationship. To write a more detailed description, click Description and then click the ellipsis (...) that appears to the right of the property field. This provides a larger area in which to write text.

  • Table Designer Category
    Expand to show information for Check Existing Data on Creation or Re-Enabling and Enforce for Replication.

  • Enforce For Replication
    Indicates whether to enforce the constraint when a replication agent performs an insert, update, or delete on this table. For more information, see Controlling Constraints, Identities, and Triggers with NOT FOR REPLICATION.

  • Enforce Foreign Key Constraint
    Specify whether changes are allowed to the data of the columns in the relationship if those changes would invalidate the integrity of the foreign key relationship. Choose Yes if you do not want to allow such changes, and choose No if you do want to allow them.

  • INSERT and UPDATE Specification Category
    Expand to show information for the Delete Rule and the Update Rule for the relationship.

  • Delete Rule
    Specify what happens if a user tries to delete a row with data that is involved in a foreign key relationship:

    • No Action   An error message tells the user that the deletion is not allowed and the DELETE is rolled back.

    • Cascade   Deletes all rows containing data involved in the foreign key relationship. Do not specify CASCADE if the table will be included in a merge publication that uses logical records. For more information about logical records, see Grouping Changes to Related Rows with Logical Records.

    • Set Null   Sets the value to null if all foreign key columns for the table can accept null values. Does not apply SQL Server 2000.

    • Set Default   Sets the value to the default value defined for the column if all foreign key columns for the table have defaults defined for them. Does not apply SQL Server 2000..

  • Update Rule
    Specify what occurs if a user tries to update a row with data that is involved in a foreign key relationship:

    • No Action   An error message tells the user that the update is not allowed and the UPDATE is rolled back.

    • Cascade   Updates all rows that contain data involved in the foreign key relationship. Do not specify CASCADE if the table will be included in a merge publication that uses logical records. For more information about logical records, see Grouping Changes to Related Rows with Logical Records.

    • Set Null   Sets the value to null if all foreign key columns for the table can accept null values. Does not apply SQL Server 2000.

    • Set Default   Sets the value to the default value that is defined for the column if all foreign key columns for the table have defaults defined for them. Does not apply SQL Server 2000.