DECLARE @AvatarURL VARCHAR(1000) = 'https://www.gravatar.com/avatar/5811b64ffd2fa7116580dafa02d9bb7b?s=360&d=identicon&r;=PG'

SELECT
    STUFF(@AvatarURL, ps.pat_start, 1, '&')
FROM
    ( VALUES (PATINDEX('%?s=[0-9][0-9]%', @AvatarURL)) ) ps (pat_start);

https://www.gravatar.com/avatar/5811b64ffd2fa7116580dafa02d9bb7b&s=360&d=identicon&r;=PG