The Dirty Secrets of NOLOCK (50 minutes)

What happens when you use NOLOCK hints in your code, or set your isolation level to READ UNCOMMITTED in SQL Server?

Try the course quiz anytime.

Learn the dirty secrets and potential uses of NOLOCK.

In this course, you’ll learn:

  • What NOLOCK means
  • Why NOLOCK can return incorrect results (and other problems)
  • What allocation order scans are (and how to get them)
  • Other risks and options for reading uncommitted data.

Course scripts are available at

This course contains closed captions in English for each video, plus a written transcript for each lesson.