Basic question(s):

Two examples: the two fields I'm joining on are of the same data type:

Example 1:
SELECT v.*
FROM visual v
INNER JOIN nameplate n
ON v.custid = n.custid AND v.upsino = n.upsino
WHERE v.custid = lcCustid
ORDER BY v.custid, v.upsino

Example2:
SELECT v.*
FROM visual v
INNER JOIN nameplate n
ON (v.custid + v.upsino) = (n.custid + n.upsino)
WHERE v.custid = lcCustid
ORDER BY v.cusid, v.upsino

Are both join conditions acceptable? Which is more efficient?

Will I get into trouble using either one? Is there a standard?

What if the join condition involves more that two fields of the same data type? Is it still OK to concatenate?

Thank You for your help.