Remove whitespace before calling the function. Use SUBSTITUTE
If you uncomment this code it would return null:
--IF @encoded_text COLLATE LATIN1_GENERAL_BIN
-- LIKE '%[^ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=]%'
-- COLLATE LATIN1_GENERAL_BIN
-- RETURN NULL
try:
SET @encoded_text = SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(
@encoded_text, ' ',''),CHAR(9),''),CHAR(10),''),CHAR(13),'')
(Okay so 5 years for me to bother to check the discussion is a bit long. I use Oracle lately...)