This WHERE Clause Quiz asks what happens when a query filters on a column alias. The answer is error 207, because WHERE runs before SELECT. A tested script shows three working fixes and a trap where an alias hides a real column.
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.
Types of Triggers Quiz: Which Trigger Can Fire on a View?
This Types of Triggers Quiz asks which trigger you can put on a view that joins two tables. The answer is INSTEAD OF INSERT. A tested script shows the error an AFTER trigger gives and how the working trigger splits one insert into two tables.
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.
SQL SERVER – A Simple Puzzle and Simple Solution of Datatype and Computed Column
An interview riddle: create two columns but give a datatype only once, and copy data without UPDATE. A computed column solves it simply.
SQL SERVER – Solution to Puzzle – Simulate LEAD() and LAG() without Using SQL Server 2012 Analytic Function
Readers found five ways to simulate LEAD() and LAG() without the SQL Server 2012 analytic functions. This post shows each solution with its author, runs all five on SQL Server 2025 and compares the rows with the real functions. Four return the same ten rows and one adds a rule of its own.
SQL SERVER – Puzzle to Win Print Book – Explain Value of PERCENTILE_CONT() Using Simple Example
Win a print book: explain the value of PERCENTILE_CONT with a simple example, and learn this SQL Server 2012 function even on an earlier version.