Re: How to max() make null as biggest value?

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 get
> null when there are null in the value list, or return the largest value as
> 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=# select * from foo;a
----1033
(2 rows)

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

there is function greatest

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

regards
Pavel Stehule

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