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Order of Operations for Update Command 2+ messages / 2 participants [nested] [flat]
* Order of Operations for Update Command @ 2016-08-25 15:27 simonwhite@dciphercomputing.com 2016-08-25 16:33 ` Re: Order of Operations for Update Command Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 1 reply; 2+ messages in thread From: simonwhite@dciphercomputing.com @ 2016-08-25 15:27 UTC (permalink / raw) To: pgsql-docs The following documentation comment has been logged on the website: Page: https://www.postgresql.org/docs/9.5/static/sql-update.html Description: Does the Update command update the columns in the order they are listed? Can an updated column's new value be used in the value calculation for a subsequent column? i.e. update mytable set qty=qty+5,price=price*1.1,subtotal=qty*price Will the subtotal be calculated based on the old column values or the new column values? -- Sent via pgsql-docs mailing list (pgsql-docs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-docs ^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Order of Operations for Update Command 2016-08-25 15:27 Order of Operations for Update Command simonwhite@dciphercomputing.com @ 2016-08-25 16:33 ` Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 2+ messages in thread From: Tom Lane @ 2016-08-25 16:33 UTC (permalink / raw) To: simonwhite@dciphercomputing.com; +Cc: pgsql-docs simonwhite@dciphercomputing.com writes: > Does the Update command update the columns in the order they are listed? Notionally, they're all done concurrently. This is embodied in our docs by defining the update source expressions thus: An expression to assign to the column. The expression can use the old values of this and other columns in the table. > Can an updated column's new value be used in the value calculation for a > subsequent column? No, see above. regards, tom lane -- Sent via pgsql-docs mailing list (pgsql-docs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-docs ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2016-08-25 16:33 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2016-08-25 15:27 Order of Operations for Update Command simonwhite@dciphercomputing.com 2016-08-25 16:33 ` Tom Lane <tgl@sss.pgh.pa.us>
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