Re: how to do this select?

In response to Yi Zhao :
> thanks Ringer.
> my mean is that:
> I want less than 2 rows which have the same value of column "b"!
>
> for example, there is 3 columns have the same value "A",
> X | A
> X | A
> Y | A
> I want my result have two of them.

I think, you are searching for DISTINCT:

test=# create table foo (a text, b text);
CREATE TABLE
test=*# copy foo from stdin;
Enter data to be copied followed by a newline.
End with a backslash and a period on a line by itself.
>> a a
>> a a
>> b a
>> \.
test=*# select distinct a,b from foo;
a | b
---+---
a | a
b | a
(2 rows)

Please, no silly top-posting.

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

Andreas
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Andreas Kretschmer
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