You can search for data in your tables by using the LIKE operator. The LIKE operator determines whether a specific character string matches a specified pattern. A pattern can include regular characters and wildcard characters.

Here is what Books On Line has on the use of wild cards

Wildcard character

Description

Example

%

Any string of zero or more characters.

WHERE title LIKE '%computer%' finds all book titles with the word 'computer' anywhere in the book title.

_ (underscore)

Any single character.

WHERE au_fname LIKE '_ean' finds all four-letter first names that end with ean (Dean, Sean, and so on).

[ ]

Any single character within the specified range ([a-f]) or set ([abcdef]).

WHERE au_lname LIKE '[C-P]arsen' finds author last names ending with arsen and starting with any single character between C and P, for example Carsen, Larsen, Karsen, and so on. In range searches, the characters included in the range may vary depending on the sorting rules of the collation.

[^]

Any single character not within the specified range ([^a-f]) or set ([^abcdef]).

WHERE au_lname LIKE 'de[^l]%' all author last names starting with de and where the following letter is not l.

Let’s take a look at some examples, first create this table and insert some data.

sql CREATE TABLE TestLike (SomeCol VARCHAR(200)) GO INSERT TestLike VALUES (‘12345’) INSERT TestLike VALUES (‘abd23bbb’) INSERT TestLike VALUES (‘abc_bb’) INSERT TestLike VALUES (‘abc______bb’) INSERT TestLike VALUES (‘zzzz’) INSERT TestLike VALUES (‘z0z0z0z0z0’) INSERT TestLike VALUES (‘bla’)


So what happens if you do the following

sql
SELECT * FROM TestLike
where SomeCol LIKE '%_%'

output

—————–

12345

abd23bbb

abc_bb

abc__bb

zzzz

z0z0z0z0z0

bla

You get back everything. This is because in a regular expression, the underscore means any single character. In order to search for an underscore, you need to put it in brackets

sql SELECT * FROM TestLike where SomeCol LIKE ‘%[_]%’


output
  
—————–
  
abc_bb
  
abc\___\___bb

Let's take a look at another example, what if you want to search for the left bracket [?

First insert the following row

sql
INSERT TestLike VALUES ('2222[2222')

Now when you do something like this

sql SELECT * FROM TestLike where SomeCol LIKE ‘%[%’


Nothing is returned. You can however put the left bracket in brackets

sql
SELECT * FROM TestLike
where SomeCol LIKE '%[[]%'

output

—————–

2222[2222

Brackets are also required for ranges. If you want to return all the rows where any of characters is 2 or 3, you can’t do this

sql SELECT * FROM TestLike where SomeCol LIKE ‘%2-3%’


You can surround that with brackets

sql
SELECT * FROM TestLike
where SomeCol LIKE '%[2-3]%'

output

—————–

12345

abd23bbb

2222[2222

You can of course also use OR

sql SELECT * FROM TestLike where SomeCol LIKE ‘%2%’ OR SomeCol LIKE ‘%3%’


But what if you want to expand that to check for a range between 2 and 6

sql
SELECT * FROM TestLike
where SomeCol LIKE '%2%'
OR SomeCol LIKE '%3%'
OR SomeCol LIKE '%4%'
OR SomeCol LIKE '%5%'
OR SomeCol LIKE '%6%'

This way is much cleaner in my opinion

sql SELECT * FROM TestLike where SomeCol LIKE ‘%[2-6]%’ ```

That is it for this post, check out the related post SQL Server does support regular expressions in check constraints, triggers are not always needed which also shows some regular expressions