út 25. 2. 2020 v 15:35 odesílatel Miles Elam <miles.e...@productops.com> napsal:
> How do you see this syntax working in a JOIN query? > > SELECT x.* EXCEPT x.col1, x.col2, y.col1 > FROM tablex AS x > LEFT JOIN tabley AS y; > > The column(s) you want to exclude become ambiguous. > Can you explain how are those column(s) ambiguous in your example? I would expect to select everything from table x (as SELECT x.* should do) except x.col1 and x.col2. Nothing is selected from table y thus y.col1 is not relevant here (the question is if this is problem or not - raise, ignore?). > Parentheses? > > SELECT x.* EXCEPT (x.col1, x.col2), y.col1 > FROM tablex AS x > LEFT JOIN tabley AS y; > > Could work, but this is encouraging the use of the wildcard selector, > which I'm not sure is a productive or maintainable goal. In exchange for > flexibility, you've added a non-trivial amount of comprehension complexity. > I'm not a big fan of the wildcard selector except in the most trivial cases > and even then only as part of development toward a final query with all > columns specified. Then again I try not to have tables with hundreds of > columns (or even tens in most cases), so my own use cases may bias > me. Personally I just don't like queries where I cannot clearly see what it > being returned to me. Anything that makes that ambiguity more popular will > be viewed with a skeptical eye. > > > On Tue, Feb 25, 2020 at 2:18 AM Stanislav Motyčka < > stanislav.moty...@gmail.com> wrote: > >> Hello, >> >> Sometimes (for tables with many columns) it would be better and easier to >> write "SELECT" statement with clause "EXCEPT": >> "SELECT * [EXCEPT col1 [,col2]] FROM ..." >> >> It's easier to write "except" one or two columns from all (*) as to write >> names of all columns besides one or two. >> What do you thin about it? >> >> Best regards >> Stano Motycka >> >>
