Re: please give me select sqls examples to distinct these!

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От David G. Johnston
Тема Re: please give me select sqls examples to distinct these!
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Msg-id CAKFQuwYvNChGg0-b+9siK0rNGj8Da-RAj3g9iy2kW=-rY1Uu8A@mail.gmail.com
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Ответ на Re: please give me select sqls examples to distinct these!  (Rob Sargent <robjsargent@gmail.com>)
Ответы Re: please give me select sqls examples to distinct these!
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On Tue, Oct 25, 2022 at 7:06 AM Rob Sargent <robjsargent@gmail.com> wrote:


On Oct 25, 2022, at 7:55 AM, jacktby@gmail.com wrote:



typedef enum SetOperation
{
    SETOP_NONE = 0,
    SETOP_UNION,
    SETOP_INTERSECT,
    SETOP_EXCEPT
} SetOperation;

Please use just text. 
What ‘dialect’ are using? In Postgres
0: select * from table
1: select * from table union select * from table is same shape
2: select * from table join table b on Id = idb 
3: select * from table except select * from tableb


#2 is probably conceptually correct but in this context should be written as:

SELECT *
FROM table
INTERSECT
SELECT *
FROM table
Distinct is a default modifier, one can specify ALL if that isn't desired.

This is trivially answered by the documentation as well:

https://www.postgresql.org/docs/current/queries-union.html

David J.

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