This Blocking and Deadlock Quiz asks which problem SQL Server ends on its own, and how the losing session finds out. A two-window test on SQL Server 2025 shows the deadlock error 1205 and the lock timeout error 1222. It also shows how to find a blocker and how to retry.
Identity Column Quiz: Why Did My IDs Skip a Number?
This Identity Column Quiz starts with three rows and one rolled-back insert, then asks what ID the next row gets. The answer is 5, not 4. A tested script proves it and shows two more ways numbers go missing.
ANSI Isolation Levels Quiz: Which Level Lets You Read Uncommitted Data?
This ANSI Isolation Levels Quiz asks which level lets one session read a price that another session has not committed. A two-window test on SQL Server 2025 shows what each level returns. It also shows how READ COMMITTED SNAPSHOT removes the wait.
Diagnosing Connection Pool Exhaustion From the SQL Server Side
Diagnose connection pool exhaustion by grouping SQL Server sessions, finding sleeping open transactions, and reading their last command.
Lost Updates: Optimistic Concurrency With a rowversion Column
Prevent lost updates with optimistic concurrency and a rowversion token, detect zero-row conflicts, and compare short locking transactions.
Destructive Reads: Pulling Work From a Queue Table With OUTPUT
Claiming a job and finishing it are two different things. Try a delete claim, a rollback, and an update claim on a tiny queue.
Optimized Locking Wait Stats: New Lock Waits in SQL Server 2025
Optimized locking wait stats are the new lock waits SQL Server 2025 records when optimized locking is on. On Night 24 at the Clipboard Diner, a new state code swaps booth cards for wristbands. Then I show what LCK_M_S_XACT_MODIFY and LCK_M_S_XACT_READ mean, how to check the setting, and why a long transaction still hurts.