LIKE operator for sequence of Numbers - sql

Question

I am trying to use wildcard expression to fetch data related to a sequence of numbers. Can I know how to use a series of numbers inside wildcard expression LIKE [0-10].
here is my query:
select grade from table where grade LIKE [1-12]?
output: is 1 and 2
I referred to t-SQL book and they talk about LIKE N[1-12]. What's the difference between LIKE [1-12] and N[1-12]?
I can use between 1 and 12 to fetch my data. But I am just curious how to use a wildcard for series of numbers with LIKE operator?

Answer 1

In SQL Server, like has three wildcards. Underscore '_' represents any single character. % represents zero or more characters. And square brackets.
The expression between the square brackets represents one single character. So,
x like '[abc]'
matches "a", "b", or "c" -- and nothing else. The following matches any digit:
x like '[0123456789]'
This, however, starts to get cumbersome to type out. So, SQL Server offers the shorthand:
x like '[0-9]'
This just means any character from the range starting with 0 and ending at 9.
You could match any hex character with:
x like '[0-9ABCDEF]'
So, additional characters are allowed in the range.
When you write
x like '[1-12]'
You are saying x like the range of characters from 1 to 1, plus the character 2. This is more easily written as:
x like '[12]'
In any case, you shouldn't store numeric values as strings, and you shouldn't use like on numbers. It is much better to write:
grade between 1 and 12
Or something like that.

Answer 2

But if you already have a column with a sequence of numbers and don't know the size, what I've done was this function:
CREATE FUNCTION Keep_Only_Int (#X VARCHAR(MAX)) RETURNS BIGINT AS BEGIN
IF #X IS NULL RETURN NULL
DECLARE #T AS INT = LEN(#X), #I AS INT = 0, #J AS CHAR(1), #RET AS VARCHAR(50) = ''
WHILE #I < #T BEGIN
SET #I += 1
SET #J = SUBSTRING(#X, #I, 1)
IF ASCII(#J) BETWEEN 48 AND 57 --Numbers, is needed because ¹, ² and ³ are going to return true in the link
SET #RET += #J
END
IF LEN(#RET) > 19 RETURN NULL --Bigger then bigint
RETURN NULLIF(#RET, '')
END
An example of usage:
create table #a (content varchar(100))
insert #a values ('My number is 123, whatever')
insert #a values ('My number is 1234, whatever')
insert #a values ('My number is ¹²³4, whatever') --> Special numbers
insert #a values ('My number is one, whatever') --> No number
insert #a values ('My number is 1234567890123456789, whatever')
insert #a values ('My number is 12345678901234567890, whatever')--> This is too big!
select *
, dbo.Keep_Only_Int(content)
from #a
The function already convert the field to BIGINT, so you can use an between statement
select *
from #a
where dbo.Keep_Only_Int(content) between 1 and 2000
It is not focused on a great performance, if you are using a table too big I'd recomend creating a specific code for that