External profiles need a stable scoped identity key. Keep mutable email values separate and reject duplicate identities.
SQL SERVER – How to ALTER CONSTRAINT
Can you ALTER CONSTRAINT in SQL Server? No. The only way to change a constraint is to drop it and create it again, and here is the script for that.
SQL SERVER – Prevent Constraint to Allow NULL
Why does a CHECK constraint allow NULL? A reader thought it was a bug. I show why it happens and how to write the constraint so NULL is rejected too.
GTIN-13 Check Digits: Validate the Final Digit in a CHECK Constraint
A GTIN-13 check digit validates a weighted checksum, not product identity. Test complete ASCII input, leading zeros and the final digit in a CHECK constraint, then see why some digit swaps still pass.
Turning a Comma-Separated Column Into a Proper Child Table
A list stuffed in one column makes every search a guess. Split it, clean it and move it into a child table, then check the result before you drop anything.
Resumable ADD CONSTRAINT in SQL Server 2022: Pausing a Primary Key Build
Use resumable ADD CONSTRAINT in SQL Server 2022 to pause a key build, inspect progress, resume safely, and understand abort behavior.
Stored Totals: Find Drift Before Repairing It
Stored totals can drift from their authoritative line amounts. This private demonstration finds two mismatches, retains empty orders and accepts valid credits. It checks decimal range before a private repair and explains why concurrency needs separate proof.