Working with Constraints
Constraints are rules that the database server enforces for you. For more information see Constraints.
For details about working with constraints, see the following topics:
| To | See |
|---|---|
| Attach a check constraint to a table to specify the data values that are acceptable in one or more columns | Attaching a New Check Constraint to a Table or Column |
| Create a constraint expression to check data for a condition | Defining a Check Constraint Expression |
| Change the constraint expression or the options that enable or disable the constraint for specific conditions | Modifying a Check Constraint |
| Apply constraints either to new data only or to existing data as well | Checking Existing Data When Creating a Check Constraint |
| Disable a check constraint when data is added to, updated in, or deleted from a table | Disabling a Check Constraint with INSERT and UPDATE Statements |
| Disable a check constraint when your table is replicated in another database | Disabling a Check Constraint for Replication |
| Remove the limitations on data values in a column | Deleting a Check Constraint |
| Ensure no duplicate values are entered in specific columns | Creating a Unique Constraint |
| Change the columns that the constraint is attached to, change the constraint name, or set additional properties for the constraint | Modifying a Unique Constraint |
| Remove the requirement for uniqueness for values entered in the column | Deleting a Unique Constraint |
| Enforce uniqueness for values entered in specified columns | Defining a Primary Key |
| Change the column order, index name, clustered option, or fill factor | Modifying a Primary Key |
| Copy column properties from a primary key column to a foreign key column to relate the two columns | Copying Column Properties to a Foreign Key Column |
| Remove the requirement for uniqueness for the values entered in a column | Deleting a Primary Key Constraint |
| See which columns participate in the foreign key side of a relationship | Viewing Foreign Key Attributes |
| Change which columns are related to columns in the primary key table | Modifying a Foreign Key |
| Check existing data when creating a relationship | Checking Existing Data when Creating a Relationship |
| Disable a foreign key constraint during INSERT and UPDATE transactions | Disabling a Foreign Key Constraint with INSERT and UPDATE Statements |
| Disable a foreign key constraint during replication of the table | Disabling a Foreign Key Constraint for Replication |
| Remove the requirement to enforce referential integrity between primary key columns and the related columns in another table | Deleting a Foreign Key Constraint |