Since yr
is just a number, you only need to extract the year from the current date:
dbo.DB_TABLE.YR <= datepart(year,{fn curdate()})-3
When writing a SQL statement in the SELECT or WHERE boxes in Designer, you are not limited to only using the functions available in the list box. Any SQL that is valid for the database can be used. The list box is only a helper, and lists commonly-used functions and statements.