_ (Wildcard - Match One Character) (Transact-SQL)
Applies To: SQL Server 2014, SQL Server 2016 Preview
Matches any single character in a string comparison operation that involves pattern matching, such as LIKE and PATINDEX.
Applies to: SQL Server (SQL Server 2008 through current version), Azure SQL Database.
The following example uses the _ operator to find all the people in the Person table, who have a three-letter first name that ends in an.
USE AdventureWorks2012; GO SELECT FirstName, LastName FROM Person.Person WHERE FirstName LIKE '_an' ORDER BY FirstName;