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From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Tue, 7 Jun 2022 18:47:17 -0700
Message-ID: 
 <CAKFQuwaY-zeoWkJwqDP6TDZnowdif2AZsT28+-SA2OWc8KXKTA@mail.gmail.com>
Subject: Re: Electricity bill
To: stercor@gmail.com
Cc: pgsql-sql <pgsql-sql@lists.postgresql.org>
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On Tue, Jun 7, 2022 at 6:39 PM Theodore M Rolle, Jr. <stercor@gmail.com>
wrote:

> I'm putting in YYYY-MM-DD dates of electricity bills and would like to no=
t
> have starting and ending dates in the same row. Only ending date.
> Will someone show me the SQL to compute the months=E2=80=99 usage? This r=
equires
> retrieving two rows to compute the number of days...
>

You can use a window function called lead (or lag) to retrieve a value from
the next (previous) row and associate it with the current row.

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 Tue, Jun 7, 2022 at 6:39 PM Theodore M Rolle, Jr. &lt;<=
a href=3D"mailto:stercor@gmail.com">stercor@gmail.com</a>&gt; wrote:</span>=
<br></div></div><div class=3D"gmail_quote"><blockquote class=3D"gmail_quote=
" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);=
padding-left:1ex"><div dir=3D"auto">I&#39;m putting in YYYY-MM-DD dates of =
electricity bills and would like to not have starting and ending dates in t=
he same row. Only ending date.<div dir=3D"auto">Will someone show me the SQ=
L to compute the months=E2=80=99 usage? This requires retrieving two rows t=
o compute the number of days...</div></div></blockquote><div><br></div><div=
 class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif">Y=
ou can use a window function called lead (or lag) to retrieve a value from =
the next (previous) row and associate it with the current row.</div><div cl=
ass=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif"><br>=
</div><div class=3D"gmail_default" style=3D"font-family:arial,helvetica,san=
s-serif">David J.</div><div class=3D"gmail_default" style=3D"font-family:ar=
ial,helvetica,sans-serif"></div></div></div>

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