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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>I prefer doing it in the FROM and not bothering using a CTE.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>So something like<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><pre>UPDATE <MY_TABLE> SET area = f.area, area_perimeter = f.area/f.perimeter<o:p></o:p></pre><pre>FROM (SELECT id, ST_Area(<GEOMETRY_COLUMN>) AS area, ST_Perimeter(<GEOMETRY COLUMN>) AS perimeter<o:p></o:p></pre><pre> FROM <MY TABLE> ) AS f<o:p></o:p></pre><pre>WHERE f.id = <MY TABLE>.id;<o:p></o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Note the FROM does not need to be the same as your table, you just need to have a common join. That makes it particularly handy for updating with aggregate values <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt'><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> postgis-users [mailto:postgis-users-bounces@lists.osgeo.org] <b>On Behalf Of </b>Marco Boeringa<br><b>Sent:</b> Sunday, September 27, 2020 1:18 PM<br><b>To:</b> postgis-users@lists.osgeo.org<br><b>Subject:</b> Re: [postgis-users] Setting multiple columns in one UPDATE request<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p>Thanks for pointing that out Alexander. I was just about to start a test after some code modifications, but now realized based on the example you pointed out that I was missing the "FROM cte" clause in my SQL statement. It feels a bit unnatural to have to specify that one, as you already define the cte name after the WITH keyword. But this example sorted it out.<o:p></o:p></p><p>Curious to see how it runs and if it leads to a measurable performance enhancement.<o:p></o:p></p><p>Marco<o:p></o:p></p><div><p class=MsoNormal>Op 27-9-2020 om 18:30 schreef Alexander Gataric:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal style='margin-bottom:12.0pt'>You have the correct link. Here's an example.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-bottom:12.0pt'><a href="https://stackoverflow.com/questions/36908495/update-with-result-from-cte-postgresql">https://stackoverflow.com/questions/36908495/update-with-result-from-cte-postgresql</a><o:p></o:p></p></div><div><p class=MsoNormal>Get <a href="http://www.bluemail.me/r?b=16117">BlueMail for Android</a> <o:p></o:p></p></div><div><p class=MsoNormal>On Sep 27, 2020, at 7:47 AM, Marco Boeringa <<a href="mailto:marco@boeringa.demon.nl" target="_blank">marco@boeringa.demon.nl</a>> wrote: <o:p></o:p></p><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><p>Hi Alexander, <o:p></o:p></p><p>I guess I could use the optional WITH clause that is part of UPDATE in PostgreSQL?:<o:p></o:p></p><div><p class=MsoNormal><a href="https://www.postgresql.org/docs/12/sql-update.html">https://www.postgresql.org/docs/12/sql-update.html</a><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>It would have been nice to see an example of such usage in the PostgreSQL help, but I'll figure it out.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Marco<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Op 27-9-2020 om 13:59 schreef Alexander Gataric:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal style='margin-bottom:12.0pt'>Rewrite to have a CTE with the area calculations and join to the table.<o:p></o:p></p></div><div><p class=MsoNormal>Get <a href="http://www.bluemail.me/r?b=16117">BlueMail for Android</a> <o:p></o:p></p></div><div><p class=MsoNormal>On Sep 27, 2020, at 2:29 AM, Marco Boeringa <<a href="mailto:marco@boeringa.demon.nl" target="_blank">marco@boeringa.demon.nl</a>> wrote: <o:p></o:p></p><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><pre>Hi all,<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>This may be an irrelevant basic question, but I just cannot find a clear <o:p></o:p></pre><pre>answer to this, there is no documentation in the PostgreSQL docs for <o:p></o:p></pre><pre>UPDATE about this:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>In case I set multiple columns using some PostGIS function that clearly <o:p></o:p></pre><pre>has a (considerable) cost associated with it, and the value of the first <o:p></o:p></pre><pre>column being set is also needed to set the second column, does <o:p></o:p></pre><pre>PostgreSQL automatically optimize this and re-use the value already <o:p></o:p></pre><pre>calculated for column 1 to set column 2's value, or is each column's SET <o:p></o:p></pre><pre>statement treated as independent entity?<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>E.g. let's say I want to calculate both area, and the division of area <o:p></o:p></pre><pre>and perimeter, like:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>UPDATE <MY_TABLE> SET area = ST_Area(<GEOMETRY_COLUMN>), area_perimeter <o:p></o:p></pre><pre>= ST_Area(<GEOMETRY_COLUMN>) / ST_Perimeter(<GEOMETRY_COLUMN>)<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Will PostgreSQL only process 'ST_Area(<GEOMETRY_COLUMN>)' once in this <o:p></o:p></pre><pre>case, thus saving CPU load, or do I need to rewrite the SQL statement <o:p></o:p></pre><pre>somehow to achieve that?<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Marco<o:p></o:p></pre><pre><o:p> </o:p></pre><pre style='text-align:center'><hr size=2 width="100%" align=center></pre><pre><o:p> </o:p></pre><pre>postgis-users mailing list<o:p></o:p></pre><pre><a href="mailto:postgis-users@lists.osgeo.org">postgis-users@lists.osgeo.org</a><o:p></o:p></pre><pre><a 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