Re: Indicating DEFAULT values in INSERT statement

From: Diego Augusto Molina <diegoaugustomolina(at)gmail(dot)com>
To: Postgres User <postgres(dot)developer(at)gmail(dot)com>
Cc: pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: Indicating DEFAULT values in INSERT statement
Date: 2011-08-09 23:47:50
Message-ID: CAGOxLdFmhwPoTbX76O-UKVvTRsd1=-e0x0LZoq6FguO-V76axw@mail.gmail.com
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Hi, when posting SQL it may be a good practice to post your PG
version so that answers may be more accurate and better fit your
needs. In this case, I don't think you'll be able to do what you are
trying to, because as of my understanding the "DEFAULT" is not part of
an expression but a keyword itself which is to be written *instead* of
an expression. I get your point and seems pretty fair to me, but if
I'm right you don't have access to the default value of the column
from within an expression.
Assuming you're using the latest stable version of PostgreSQL (9.0
as of today), you can check the following page for an online reading
reference of the INSERT statement:
http://www.postgresql.org/docs/9.0/interactive/sql-insert.html
If you look carefully, you'll see that for the value of a column you
may write: the "DEFAULT" keyword [exclusive or] an expression (which
includes specific values).
The [exclusive or] is deduced because of the pipe (`|') between the
two choices which are embraced by curly braces.
So, if you were able to use the "DEFAULT" keyword inside an
expression, instead of having the "{ expression | DEFAULT }" syntax
you would have the "expression" syntax, which would include the case
of having just "DEFAULT" as an expression. It's just a matter of
understanding the syntax.

Cheers!

--
Diego Augusto Molina
diegoaugustomolina(at)gmail(dot)com

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