NOLOCK is bad and you probably shouldn’t use it, but every time I mention that publicly, the pushback just keeps coming. I don’t know why people so firmly believe that their situation couldn’t possibly be affected by bad/random data from NOLOCK.
Today’s misconception comes from a LinkedIn commenter telling me it’s safe to use if you’re doing index seeks. Hoo boy. Let’s whip up a table with an index:
DROP TABLE IF EXISTS dbo.NolockTest; CREATE TABLE dbo.NolockTest (Id INT IDENTITY(1,1) PRIMARY KEY CLUSTERED, Label VARCHAR(20), Score INT); CREATE INDEX Label ON dbo.NolockTest(Label); INSERT INTO dbo.NolockTest(Label, Score) SELECT CASE WHEN value %