On 2016/03/09 10:01 PM, David Raymond wrote: > For my own clarification, the statements quoted way down below aren't exactly > equivalent, correct? > > "For each pair of columns identified by a USING clause, the column from the > right-hand dataset is omitted from the joined dataset. This is the only > difference between a USING clause and its equivalent ON constraint." > > (Short version: USING will return fewer fields than ON, and order can matter > for both types because of affinity/collation)
Indeed so - the USING optimises the columns out that are coincidental (by assuming duplication would be unwanted) when you request the asterisk column wildcard, as I did in the examples. I should have been more specific in that it is the result-set that is algebraically equivalent. This per-chance column layout should however never be depended on, always specify the columns that you want in the results in any production query. Thanks, good to point this out to prospective USING users! :) Cheers, Ryan
