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 – How to Use Decode in SQL Server?
CASE expresses the DECODE mapping in this SQL Server example. I keep the named matches and default value explicit.
SQL SERVER – Potential Bottlenecks for Performance
At GIDS I was asked to name potential bottlenecks for performance. My old college list still holds: CPU, RAM, hard disk, network and application code.
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.
Common Table Expressions for Readability
Common table expressions for readability name query steps and support recursion, but they do not promise cached intermediate results.
geometry STDistance: Measure the Closest Points of Two Shapes
geometry STDistance measures the shortest distance between points belonging to two represented shapes. I compare an interior gap with an endpoint gap. Intersecting shapes provide a useful zero-distance case.
SELECT * in Production Code: The Hidden Costs
See the real costs of SELECT * in production code: lost covering indexes, lookups, stale view metadata, broken inserts and wider results.