Error Code: 1172. Result consisted of more than one row INSIDE A FUNCTION

[Nestor Pedraza]

Hello everybody thanks you in advance. I’m getting this error message when I run a user defined function .
The function just read from a table the EURO exchange value for a certain date. There is a unique result for each date, but keep given me the message .
Here is the code

CREATE DEFINER=`myNestor`@`%` FUNCTION `EURO`(FEC DATE ) RETURNS decimal(11,2)
BEGIN
SET @TODAY=FEC;
SELECT EURO FROM DATA.IYM WHERE DOER=@HOY INTO @RESULT ;
RETURN @RESULT ;
END