SELECT

mt.##col1##, ..., jt.##co11##, ...

FROM dbo.maintable mt

LEFT OUTER JOIN jointable jt ON

--ignore last two bytes of patid if they are alpha, because it's a state abbrev, not part of key value

jt.key = LEFT(mt.patid, LEN(mt.patid) - CASE WHEN RIGHT(mt.patid, 2) LIKE '[a-z][a-z]' THEN 2 ELSE 0 END)

Edit: Added sql code tags to colorize code.