The first version will work for any backend not only VFP. Efficiency (optimization) will depends on what indexes you have on tables.

>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.