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Date: Tue, 20 Apr 2010 17:17:53 +0200
Message-ID: <s2z162867791004200817j80b0a976u9979bfc7e7d73f25@mail.gmail.com>
Subject: Re: How to max() make null as biggest value?
From: Pavel Stehule <pavel.stehule@gmail.com>
To: Feixiong Li <feixiongli@gmail.com>
Cc: pgsql-sql@postgresql.org
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Hello

2010/4/14 Feixiong Li <feixiongli@gmail.com>:
> Hi , guys ,
>
> I am newbie for sql, I have a problem when using max() function, I need g=
et
> null when there are null in the value list, or return the largest value a=
s
> usual, who can do this?
>

max()  returns max value of some column

create table foo(a int);
insert into foo values(10);
insert into foo values(33);

postgres=3D# select * from foo;
 a
----
 10
 33
(2 rows)

Time: 0,524 ms
postgres=3D# select max(a) from foo;
 max
-----
  33
(1 row)

there is function greatest

postgres=3D# select greatest(1,2,34,2,1);
 greatest
----------
       34
(1 row)

regards
Pavel Stehule

> i.e. =C2=A0max([1,2,3,4,5]) =3D> 5
> max([1,2,3,4,5,null]) =3D> null
>
> thanks in advance!
>
> Feixiong
> feixiongli@gmail.com
>
>
>
>
>
>
>
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