[ ] (Wildcard - Character(s) to Match) (Transact-SQL)
Matches any single character within the specified range or set that is specified between the brackets. These wildcard characters can be used in string comparisons that involve pattern matching, such as LIKE and PATINDEX. For more information, see Pattern Matching in Search Conditions.
The following example uses the  operator to find the IDs and names of all Adventure Works employees who have addresses with a four-digit postal code.
USE AdventureWorks; GO SELECT e.EmployeeID, c.FirstName, c.LastName, a.PostalCode FROM HumanResources.Employee AS e INNER JOIN Person.Contact AS c ON e.ContactID = c.ContactID INNER JOIN HumanResources.EmployeeAddress AS ea ON e.EmployeeID = ea.EmployeeID INNER JOIN Person.Address AS a ON a.AddressID = ea.AddressID WHERE a.PostalCode LIKE '[0-9][0-9][0-9][0-9]'; GO
Here is the result set:
EmployeeID FirstName LastName PostalCode ---------- --------- --------- ---------- 290 Lynn Tsoflias 3000