How to escape underscore character in PATINDEX pattern argument?
Solution 1:
I've always done it with brackets: '%[_]%'
Solution 2:
To match two underscores, each must be bracketed
'%[__]%' -- matches single _ with anything after
'%[_][_]%' -- matches two consecutive _
Solution 3:
You can escape using the [ and ] characters like so:
PRINT PATINDEX('%[_]%', '37_21')