A reader wanted students and courses grouped by course and instructor in a single row. Here is a simple concatenation trick with XML PATH that does it.
What Is a Deadlock in SQL Server?
A deadlock in SQL Server is two sessions each holding what the other needs. I caused one on purpose and read error 1205. Why it is not the same as blocking, who gets killed, and the boring fix that works.
Cannot Resolve the Collation Conflict (Msg 468): SQL in Sixty Seconds #047
Cannot resolve the collation conflict is Msg 468, and it appears when two text columns use different collations. I reproduced it on SQL Server 2025 with a temp table, found the mismatched columns with a query and tested three fixes, from a COLLATE clause in the query to changing the column itself.
Overlapping Indexes With INCLUDE Columns: Merging Them Safely
Find overlapping indexes, compare ordered keys and INCLUDE lists, merge coverage carefully, and review usage before removing either index.
Plan Cache Duplicates From Whitespace and Case Differences
One extra space or a lowercase keyword gives you a second cached plan. See it in the cache, and learn what actually fixes it.
Where T-SQL Differs From the ANSI Standard
See where T-SQL differs from the ANSI standard in row limits, concatenation, NULL behavior, and practical query portability.
Temp Table Scope in Nested Procedures and Dynamic SQL
Explain temp table scope across nested procedures and dynamic SQL, reproduce missing and duplicate-name errors, and pass rows safely.