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From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Thu, 6 Jul 2023 09:09:36 -0700
Message-ID: 
 <CAKFQuwZuhDQ3GsQLreBB15SvehBRz_iJhFoo-qxgtAgmiEXSOQ@mail.gmail.com>
Subject: Re: How to select the last value/row?
To: Shaozhong SHI <shishaozhong@gmail.com>
Cc: pgsql-sql <pgsql-sql@lists.postgresql.org>
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On Thu, Jul 6, 2023 at 9:02=E2=80=AFAM Shaozhong SHI <shishaozhong@gmail.co=
m> wrote:

>
> How about
> ID
> 5
> 4
> 3
> 3
> 2
> 3
>
> The last is 3.
>
>
There is no concept of "last" in a query unless you define an order.  If
you really want whatever row really happens to randomly show up in the last
result row the use the "row_number()" window function to give each row a
number and then sort and limit on that.

David J.

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<div dir=3D"ltr"><div dir=3D"ltr"><div class=3D"gmail_default" style=3D"fon=
t-family:arial,helvetica,sans-serif"><span style=3D"font-family:Arial,Helve=
tica,sans-serif">On Thu, Jul 6, 2023 at 9:02=E2=80=AFAM Shaozhong SHI &lt;<=
a href=3D"mailto:shishaozhong@gmail.com">shishaozhong@gmail.com</a>&gt; wro=
te:</span><br></div></div><div class=3D"gmail_quote"><blockquote class=3D"g=
mail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204=
,204,204);padding-left:1ex"><div dir=3D"ltr"><div dir=3D"ltr"><br></div><di=
v class=3D"gmail_quote"><div>How about=C2=A0</div><div>ID</div><div>5</div>=
<div>4</div><div>3</div><div>3</div><div>2</div><div>3</div><div><br></div>=
<div>The last is 3.</div><div><br></div></div></div></blockquote><div><br><=
/div><div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans=
-serif">There is no concept of &quot;last&quot; in a query unless you defin=
e an order.=C2=A0 If you really want whatever row really happens to randoml=
y show up in the last result row the use the &quot;row_number()&quot; windo=
w function to give each row a number and then sort and limit on that.</div>=
<div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-seri=
f"><br></div><div class=3D"gmail_default" style=3D"font-family:arial,helvet=
ica,sans-serif">David J.</div><div class=3D"gmail_default" style=3D"font-fa=
mily:arial,helvetica,sans-serif"></div></div></div>

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