SELECT * FROM (T1 JOIN T2 USING (A)) JOIN T3 USING (A)The columns returned by the first join operator, T1 JOIN T2 USING (A), are: A, T1.B, T1.C, T2.B, T2.C (note: the column in the USING clause is only returned once, even though it exists both in T1 and T2)
That's a subtle aspect of USING that I wasn't previously aware of. Thanks much for the clear explanation of the feature's behavior! bryan
