Enforce case-insensitive unique user names in a case-sensitive database using an indexed computed column with an explicit collation.
Checking Constraints After a Bulk Load With DBCC CHECKCONSTRAINTS
Run DBCC CHECKCONSTRAINTS after a controlled bulk-load bypass, inspect violations, and restore enabled trusted CHECK and foreign-key rules.
NOCHECK CONSTRAINT: Loading Data and Trusting Foreign Keys Again
Use NOCHECK CONSTRAINT carefully, distinguish enabled from trusted foreign keys, validate old rows, and restore optimizer assumptions.
A Unique Constraint That Allows Many NULLs
Allow many NULLs while enforcing unique non-NULL values with a filtered SQL Server index, required SET options, and tested queries.
Self-Referencing Foreign Keys: Managers, Employees and Deletes
Delete a manager and SQL Server says no, which is good. See how to reassign reports safely and how to catch loops the foreign key allows.
Handling Duplicate Key Errors 2627 and 2601 in a CATCH Block
Handle duplicate key errors 2627 and 2601 in TRY CATCH, preserve unexpected errors, and avoid racing existence checks during inserts.
SQL SERVER – Find Untrusted Foreign Key
An Untrusted Foreign key has not validated all existing rows. A customer bulk-load history prompted this inventory.