_ (Wildcard - Match One Character) (Transact-SQL)
Matches any single character in a string comparison operation that involves pattern matching, such as LIKE and PATINDEX. For more information, see Pattern Matching in Search Conditions.
The following example uses the _ operator to find all the people in the
Contact table, who have a three-letter first name that ends in
USE AdventureWorks; GO SELECT FirstName, LastName FROM Person.Contact WHERE FirstName LIKE '_an' ORDER BY FirstName;