Re: how to set a DEFAULT value !!


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Which database server is this?

This is definitely the behavior of MySQL, PostgreSQL, and Oracle,
and I'm pretty sure most others follow it as well.

And, can you omit the name of the column you want defaulted, and does this
server then insert the default value?

Yes. One way to think about this is to realize that *all* columns have
an automatic default of NULL, we are just changing it to something a
little more useful:

CREATE TABLE foo (
a int,
b int DEFAULT 22,
c int DEFAULT stockprice('RHAT')
);

is completely identical to:

CREATE TABLE foo (
a int DEFAULT NULL,
b int DEFAULT 22,
c int DEFAULT stockprice('RHAT')
);


-- A PostgreSQL example.
-- stockprice() is a pl/perl function that returns the real-time value
-- (in cents) of RedHat stock via a web service.

INSERT INTO foo(b) VALUES (14);

SELECT * FROM foo;

a | b | c
---+----+------
| 14 | 3025

-- We triggered the DEFAULT values of both a and c because we did
-- not specify them


INSERT INTO foo(a,b,c) VALUES (7,DEFAULT,47);

SELECT * FROM foo;

a | b | c
---+----+------
| 14 | 3025
7 | 22 | 47

-- We told b to use its default value explicitly


INSERT INTO foo(a,b,c) VALUES (DEFAULT,DEFAULT,NULL);

SELECT * FROM foo;
a | b | c
---+----+------
| 14 | 3025
7 | 22 | 47
| 22 |


-- We told a and b to use their default values, and set c explicitly


It's late here, so hope that made sense. :)

--
Greg Sabino Mullane greg@xxxxxxxxxxxx
PGP Key: 0x14964AC8 200604270030
http://biglumber.com/x/web?pk=2529DF6AB8F79407E94445B4BC9B906714964AC8
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