SQL Server - Constraints
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The presentation covers database constraints including primary keys, unique constraints, check constraints, default constraints, and foreign keys. It discusses their roles in ensuring data integrity, with examples of each type. Additionally, resources like presentation recordings and slides are provided for further reference.
SQL Server - Constraints
- 1. Constraints Presentation by Aaron Buma Dev Lead and DBA
- 3. Primary Key Constraint •Most common constraint •Doesn’t allow NULL or duplicates •There can only be one per table
- 4. Unique Constraint •Can be used when a table already has a Primary Key •Does not allow duplicates, but DOES allow a NULL
- 5. Check Constraint •Enforces domain integrity, data must conform •Can refer to a single or multiple columns •Example: column value must be > 3.
- 6. Default Constraint •Useful for inserting data into “NOT NULL” columns •Can be dynamic, example: Using GETDATE() •Can be overridden with actual values
- 7. Foreign Key Constraint •A value in the FK’d table exists as a Primary Key of a table, usually a different one •Verifies constraint on EXISTING data and NEW data – “WITH NOCHECK” only verifies NEW data
- 8. Data Integrity •Domain Integrity (Constraint on individual value) – Check Constraints •Entity Integrity (Looks at entire table) – Primary Keys, Unique Constraints •Referential Integrity (must exist in other table) – Foreign Keys
- 9. DEMOS
- 10. Review • Constraints • Data Integrity Presentation Recording, Slides and Scripts – Available at: http://www.AaronBuma.com