Use value from select in same query

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April 7th, 2008, 12:42 PM

boba5555

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Use value from select in same query

Hello,

I want to do something like this
UPDATE mytable m SET m.value = (SELECT SUM(l.val) FROM list l WHERE m.id = l.id) * 3;

I've tried this, but it doesn't work. I thought about using GROUP BY, but I am not so sure how that will help. Can someone help me?

Thank you.

April 7th, 2008, 02:26 PM

mehere

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try this:

Code:

update mytable 
set value = strUpdate.sum_Value
from mytable m inner join
	(select id, sum(val) as sum_Value
	from list group by id)
as strUpdate
on m.id = strUpdate.id

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April 7th, 2008, 04:29 PM

boba5555

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Quote:

Originally Posted by mehere

try this:

Code:

update mytable 
set value = strUpdate.sum_Value
from mytable m inner join
	(select id, sum(val) as sum_Value
	from list group by id)
as strUpdate
on m.id = strUpdate.id

I think I still need help :|
This is my complete query (of course, with your suggestion)

Code:

UPDATE links SET ratio = (incl.cSUM + 1.0) / (outcl.cSUM + 1.0) 
FROM links l INNER JOIN (SELECT link, SUM(cnt) AS cSUM FROM 
inclicks GROUP BY link) AS incl on l.id = incl.link INNER JOIN 
(SELECT link, SUM(cnt) AS cSUM FROM outclicks GROUP BY link) 
AS outcl on l.id = outcl.link;

And when I try to start that I am getting message
"MySQL][ODBC 3.51 Driver][mysqld-5.0.45-log]You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM links l INNER JOIN (SELECT link, SUM(cnt) AS cSUM FROM inclicks GROUP BY li' at line 1"

I was looking on net for tutorial about inner join and I have found (and understand) I will get temporary table that contains 'links', 'inclicks' and 'outlicks' (in my case these tables) and one row that correspond to l.id. But how ratio knows which row to take? So, with join I should have
l.id | incl.cSUM | outcl.cSum
-----------------------------
1 | 10 | 20
-----------------------------
2 | 3 | 15
-----------------------------
5 | 8 | 33
-----------------------------

But how ratio for id = 5 will know that it is equal to 9 / 34. I believe that should work, but I don't understand why. I will understand if there is something like this

UPDATE links l1 SET [other part of query] WHERE l.id = l1.id;

but there is not.

Thank you.

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