<= (Less Than or Equal To) (Transact-SQL)
Compares two expressions (a comparison operator). When you compare nonnull expressions, the result is TRUE if the left operand has a value lower than or equal to the right operand; otherwise, the result is FALSE.
Unlike the = (equality) comparison operator, the result of the >= comparison of two NULL values does not depend on the ANSI_NULLS setting. If either or both of the expressions are NULL, the result is always FALSE.
expression <= expression
Is any valid expression. Both expressions must have implicitly convertible data types. The conversion depends on the rules of data type precedence.