Andy Mallon digs into one scenario in which you shouldn’t assume how ISNUMERIC behaves:
Someone posted to #sqlhelp on Twitter, asking the following: “Wondered if anyone could enlighten me as to why ISNUMERIC(‘7d8’) returns 1?”
Sure enough,
SELECT ISNUMERIC('7d8')returns a 1.
Great answer and explanation, and his advice to use TRY_CONVERT() for 2012 and up is spot-on.