Question

I have an interesting behavior that I would like to better understand so I don’t get hung up misusing it by accident.

The following is an example of escaping a ‘%’ in a WHERE clause:

select * from #z where b like '%e%' ESCAPE 'e'

In this table with these values:

create table #z (a int, b varchar(10))
insert into #z values (1, 'e25%')
insert into #z values (2, '25')
insert into #z values (3, '18%')
insert into #z values (4, 'cab')
insert into #z values (5, '2%')

selects the three rows with the % at the end.

However, if I replace like '%e%' with like 'ee%' it selects only the first row. Thus it appears that double-escaping the % is like a double-negative, and undoes the escape, thus making the % back into the wildcard again. Am I understanding this correctly? Or is there something else going on here?

Answer 1

I don’t actually use ESCAPE: I’ve always found it odd.
In this case, you’re escaping the 2nd e so you get like 'e%' (with no escape)

Personally, I’d use this like '%[%]' (with no escape) where possible