SQL Server Escape an Underscore

How do I escape the underscore character?

I am writing something like the following where clause and want to be able to find actual entries with _d at the end.

Where Username Like '%_d'

T-SQL Reference for LIKE:

> You can use the wildcard pattern matching characters as literal characters. To use a wildcard character as a literal character, enclose the wildcard character in brackets. The following table shows several examples of using the LIKE keyword and the [ ] wildcard characters.

For your case:

... LIKE '%[_]d'

Obviously @Lasse solution is right, but there's another way to solve your problem: T-SQL operator LIKE defines the optional ESCAPE clause, that lets you declare a character which will escape the next character into the pattern.

For your case, the following WHERE clauses are equivalent:

WHERE username LIKE '%[_]d';            -- @Lasse solution
WHERE username LIKE '%$_d' ESCAPE '$';
WHERE username LIKE '%^_d' ESCAPE '^';

I had a similar issue using like pattern '%_%' did not work - as the question indicates :-)

Using '%\_%' did not work either as this first \ is interpreted "before the like".

Using '%\\_%' works. The \\ (double backslash) is first converted to single \ (backslash) and then used in the like pattern.

These solutions totally make sense. Unfortunately, neither worked for me as expected. Instead of trying to hassle with it, I went with a work around:

select *
from information_schema.columns 
where replace(table_name,'_','!') not like '%!%'
order by table_name

This worked for me, just use the escape '%\_%'

Adding [ ] did the job for me

like '%[\\_]%'

None of these worked for me in SSIS v18.0, so I would up doing something like this:

WHERE CHARINDEX('_', thingyoursearching) < 1

..where I am trying to ignore strings with an underscore in them. If you want to find things that have an underscore, just flip it around:

WHERE CHARINDEX('_', thingyoursearching) > 0

Adding to Gerardo Lima's answer, I was having problems when trying to use backslash as my escape character for the ESCAPE clause. This caused issues:

SELECT * FROM table WHERE email LIKE '%@%\_%' ESCAPE '\'

It was resolved by switching to an exclamation point. This worked:

SELECT * FROM table WHERE email LIKE '%@%!_%' ESCAPE '!'