Tag: T-SQL

July 20, 2026

Fix “Msg 207: Invalid Column Name” in SQL Server

Troubleshooting

🚨Part of the SQL Server Errors series, the exact messages and what actually causes them. Msg 207 · Level 16 · State 1 Invalid column name ‘X’. ⚡The column does not exist in the context the query is running in. Before assuming a typo, check you are on the database you think you are on,…

Written by

Peter Whyte
May 8, 2026

What WITH (NOLOCK) Actually Does in SQL Server

T-SQL Fundamentals

Almost every SQL Server developer has copied WITH (NOLOCK) onto the end of a query at some point, usually because someone said it “makes queries faster” or “avoids blocking.” Both of those things are technically true. What rarely gets explained is what you’re trading away to get them. WITH (NOLOCK) doesn’t make a query faster…

Written by

Peter Whyte
February 16, 2026

Get Current Date & Time in SQL Server

T-SQL Fundamentals

Getting the current date and time in SQL Server is straightforward. Choosing the correct function for your workload is what matters. Whether you’re stamping audit rows, logging ETL runs, or investigating production issues, SQL Server exposes several built-in functions with different precision and return types. All of these functions use the Windows OS clock of…

Written by

Peter Whyte
February 8, 2026

How to Kill a SPID in SQL Server

T-SQL Fundamentals

In SQL Server, every connection to the database engine is assigned a Session Process ID, commonly known as a SPID. There are situations where you may need to kill a SPID in SQL Server. This typically occurs when a session is blocking other queries, running indefinitely, holding locks during maintenance, or preventing a database from…

Written by

Peter Whyte
February 7, 2026

How to Check Blocking SPIDs in SQL Server

Performance Tuning

Blocking is one of the most common causes of performance issues in SQL Server. When one session holds a lock on a resource and another session needs that same resource, the second session waits. If that wait persists, users experience slowness. Understanding how to quickly identify blocking SPIDs is a core DBA skill. This guide…

Written by

Peter Whyte
January 14, 2026

Deleting Rows in Batches in SQL Server

T-SQL Fundamentals

Deleting large volumes of data from a SQL Server table looks simple, but it can cause real problems if done carelessly. A single large DELETE can: When you’re cleaning up historical data or running routine maintenance, deleting rows in batches is usually the safest and most predictable approach. This post shows a simple, production-safe pattern…

Written by

Peter Whyte
January 12, 2026

RAND() vs NEWID() in SQL Server

T-SQL Fundamentals

Most people searching for “random numbers in SQL Server” want one of two things: SQL Server gives you two common tools for this: RAND() and NEWID(). They solve different problems, and confusion usually starts when they are treated as interchangeable. This post shows how to use both, starting with simple examples, and explains why they…

Written by

Peter Whyte
January 7, 2026

Applying Data Retention Safely in SQL Server

Maintenance

Data retention in SQL Server usually means deleting old data in a controlled and repeatable way. That might be driven by compliance requirements, table growth that’s starting to hurt performance, SQL Server Express size limits, or simply keeping log and audit tables under control. Whether this is a one-off cleanup or a permanent maintenance task,…

Written by

Peter Whyte
January 5, 2026

Understanding WHERE 1=1 and WHERE 1=2 in SQL Queries

T-SQL Fundamentals

In SQL, you will often see queries written using WHERE 1=1 or WHERE 1=2. At first glance, both look pointless. One is always true, the other always false. In practice, both are deliberate patterns used for query construction and control, not filtering logic. They exist to make SQL safer, easier to manipulate, and more predictable…

Written by

Peter Whyte
January 1, 2026

What the USE Command Does in SQL Server

T-SQL Fundamentals

The USE command changes the database context for the current session. Every statement in SQL Server runs in the context of a database. When you run USE, you are telling SQL Server which database subsequent statements should execute against until the context changes again or the session ends. That single behaviour explains a lot of…

Written by

Peter Whyte