{"id":1270,"date":"2026-07-11T23:56:40","date_gmt":"2026-07-11T18:26:40","guid":{"rendered":"https:\/\/lastroundai.com\/blog\/?post_type=iq&p=1270"},"modified":"2026-07-19T09:23:29","modified_gmt":"2026-07-19T03:53:29","slug":"sql-server","status":"publish","type":"iq","link":"https:\/\/lastroundai.com\/interview-questions\/sql-server","title":{"rendered":"SQL Server Interview Questions (2026): T-SQL & Performance Q&A"},"content":{"rendered":"

Microsoft SQL Server sits behind roughly 30.9% of the databases professional developers reported using in the 2025 Stack Overflow Developer Survey<\/a>, still the fourth most-used database in that list behind PostgreSQL, MySQL, and SQLite. That number undersells how many interviews actually touch it, because a huge share of .NET, enterprise, and internal-tooling roles run on SQL Server even when the job posting just says “SQL.” Candidates walk in ready to talk about joins and get asked why a stored procedure with a table variable is ten times slower than the same query written with a temp table, and that’s a different conversation entirely.<\/p>\n

This page is scoped to T-SQL and SQL Server internals specifically, not generic ANSI SQL. If you’re prepping for a PostgreSQL or MySQL role, our general SQL interview questions<\/a> guide covers joins, subqueries, and window functions in database-agnostic syntax instead. Everything here assumes you’re sitting down in front of SSMS, Azure Data Studio, or a connection string pointed at an actual SQL Server or Azure SQL instance.<\/p>\n

My honest opinion: prep guides spend too much time on CREATE PROCEDURE syntax and not enough on execution plans. You can learn stored procedure syntax in twenty minutes from the docs. Reading a plan well enough to explain why the optimizer picked a table scan over a seek takes real practice, and it’s the actual skill that separates someone who can debug a slow production query from someone who can only recite definitions.<\/p>\n

These SQL Server interview questions cover twenty-seven items across ten areas: T-SQL basics and how they diverge from ANSI SQL, clustered versus non-clustered indexes and covering indexes, reading execution plans and sargability, stored procedures versus functions, CTEs and window functions, transactions and isolation levels, locking and deadlocks, temp tables versus table variables versus CTEs, DELETE versus TRUNCATE, and the performance problems that actually show up in production. Every code sample is T-SQL, tested against the syntax SQL Server 2019 and later actually accepts.<\/p>\n

55<\/span>Questions<\/span><\/div>
Indexes & Execution Plans<\/span>Core Topic<\/span><\/div>
T-SQL & DMV Queries<\/span>Format<\/span><\/div>
Read Committed<\/span>Default Isolation<\/span><\/div><\/div>\n

T-SQL basics: what actually diverges from ANSI SQL<\/h2>\n

Nobody fails an interview on this section alone, but a shaky answer here signals you’ve only ever worked against MySQL or Postgres and copy-pasted your way through a SQL Server task once.<\/p>\n

<\/span>Easy questions<\/h2>17<\/span><\/div>
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