DECLARE @lengthtest VARCHAR(15)

-- plain text
SET @lengthtest = 'testing'
SELECT @lengthtest, LEN(@lengthtest), DATALENGTH(@lengthtest)

-- add 3 empty spaces
SET @lengthtest = 'testing   '
SELECT @lengthtest, LEN(@lengthtest), DATALENGTH(@lengthtest)

-- add a special character ®
SET @lengthtest = 'testing'+char(0174)
SELECT @lengthtest, LEN(@lengthtest), DATALENGTH(@lengthtest)

-- add a non-visible special character, a carriage return for example
SET @lengthtest = 'testing'+CHAR(13)
SELECT @lengthtest, LEN(@lengthtest), DATALENGTH(@lengthtest)

-- remember, datatype matter too! NVarchar stores in 2 bit blocks, so your datalength will usually be near double the len value
DECLARE @Nlengthtest NVARCHAR(15)

-- plain text
SET @Nlengthtest = N'testing'
SELECT @Nlengthtest, LEN(@Nlengthtest), DATALENGTH(@Nlengthtest)


-- both functions also work with other data types, like integers!
DECLARE @Ilengthtest int

SET @Ilengthtest = 1234567
SELECT @Ilengthtest, LEN(@Ilengthtest), DATALENGTH(@Ilengthtest)
-- not the len is the actual length of the number, but the datalength is how much space is being used to store it.