SQL Interview: 71 Potential issues with NOLOCK

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database.

Section: Administration Level: Advanced

Question:

You have applications that make extensive use of NOLOCK hints. You have heard that this can cause issues.

Which of the following issues could occur as a result of using NOLOCK hints?

• Duplicate rows
• Phantom rows
• Missing rows

Answer:

All three issues can occur when NOLOCK hints are used.

2025-08-16