How to escape a string for use with the LIKE opera

问题:

I am looking for something that works in SQL Server similar to the @ symbol in c# which causes a string to be taken as it's literal. Eg:

string text = "abcd\\efg";
Output of text = abcd\efg

string text = @"abcd\\efg";
Output of text = abcd\\efg

Note how the @ affected the string to take every character as is.

Now I am not sure this is possible but here is my issue and maybe there is a better way to solve this. Consider the following basic query:

SELECT [Name] 
  FROM [Test] 
 WHERE [Name] LIKE (@searchText + '%')

My issue is if they put a %, _ or any other of those special characters that can affect my like clause. I want the match to act just like a 'starts with' function. So is there anything I can apply to the @searchText to say take this literally or is there possbibly a better solution that I am not thinking of?

Edit: I do not want the solution to be client side cleaning. I need this stored proc to work without relying on the data being passed in being cleaned.

回答1:

To search for "%" as a literal not wildcard in a string, it needs escaped as [%].

Now, SQL Server only need 3 characters escaping: % _ [

So, create a scalar udf to wrap this:

REPLACE(REPLACE(REPLACE(@myString, '[', '[[]'), '_', '[_]'), '%', '[%]')

Because of the simplicity (aka: very limited) pattern matching in SQL, nothing more complex is needed...

回答2:

In TSQL, you can wrap the % and _ characters in brackets like so [%] [_] this tells SQL to treat them as literals.

I have tested and verified this works in SQL Server 7.0, 2000, and 2005.

http://msdn.microsoft.com/en-us/library/aa933232(SQL.80).aspx

回答3:

Each character to be treated literally should be enclosed in square brackets. A right bracket is taken literally directly so don't enclose that one.

回答4:

If you parameterize your query you don't need to worry about it.

UPDATE

As recursive stated in the comments, % still needs to be escaped even in parameterized queries, I didn't realize linq to sql was doing it automagically when I tested.

You can use ESCAPE 'x' where x is the character you wish to be the escape character. Linq to SQL does it like this

WHERE [Name] LIKE @searchText ESCAPE '~'

where @searchText = [some text with a~% character%]

or as others have stated it can be escaped with [%]

view the documentation

回答5:

I'd sanitize the string in the front-end application rather than try and do hokey stuff in SQL to work around this.

回答6:

From the docs:

Syntax

match_expression [ NOT ] LIKE pattern [ ESCAPE escape_character ]

Use the ESCAPE option like so:

SELECT [Name] 
  FROM [Test] 
 WHERE [Name] LIKE (REPLACE(@searchText, '%', '%%') + '%') ESCAPE '%'

回答7:

If you don't want to modify the incoming text, you can use the "LEFT" function to create your own "STARTSWITH":

SELECT [Name] 
  FROM [Test] 
 WHERE @searchText = LEFT( [Name], LEN( @searchText ) )

(Note that you probably need to do extra work to handle the case of NULLs or empty string.)

EDIT: Removed the incorrect statement about using "LIKE" to search for "%".