Update with Sub Query Derived Table Error - sql

Question

I have the following SQL statement to simply update the #temp temp table with the latest package version number in our Sybase 15 database.
UPDATE t
SET versionId = l.latestVersion
FROM #temp t INNER JOIN (SELECT gp.packageId
, MAX(gp.versionId) latestVersion
FROM Group_Packages gp
WHERE gp.groupId IN (SELECT groupId
FROM User_Group
WHERE userXpId = 'someUser')
GROUP BY gp.packageId) l
ON t.packageId = l.packageId
To me (mainly Oracle & SQL Server experience more than Sybase) there is little wrong with this statement. However, Sybase throws an exception:
You cannot use a derived table in the FROM clause of an UPDATE or DELETE statement.
Now, I don't get what the problem is here. I assume it is because of the aggregation / GROUP BY being used. Of course, I could put the sub query in a temp table and join on it but I really want to know what the 'correct' method should be and what the hell is wrong.
Any ideas or guidance would be much appreciated.

Answer 1

It seems that SYBASE doesn't support nested queries in UPDATE FROM class. Similar problem
Try to use this:
UPDATE #temp
SET versionId = (SELECT MAX(gp.versionId) latestVersion
FROM Group_Packages gp
WHERE gp.packageId=#temp.packageId
and
gp.groupId IN (SELECT groupId
FROM User_Group
WHERE userXpId = 'someUser')
)
And also what if l.latestVersion is NULL? Do you want update #temp with null ? if not then add WHERE:
WHERE (SELECT MAX(gp.versionId)
....
) is not null

Answer 2

I guess this is a limitation of Sybase (not allowing derived tables) in the FROM clause of the UPDATE. Perhaps you can rewrite like this:
UPDATE t
SET t.versionId = l.versionId
FROM #temp t
INNER JOIN
Group_Packages l
ON t.packageId = l.packageId
WHERE
l.groupId IN ( SELECT groupId
FROM User_Group
WHERE userXpId = 'someUser')
AND
l.versionId =
( SELECT MAX(gp.versionId)
FROM Group_Packages gp
WHERE gp.groupId IN ( SELECT groupId
FROM User_Group
WHERE userXpId = 'someUser')
AND gp.packageId = l.packageId
) ;

Answer 3

Your table alias for #temp is called "t" and your original table is called "t".
My guess is that this is the problem.
I think you want to start with:
update #temp

Answer 4

Does this syntax work in Sybase?
update dstTable T
set (T.field1, T.field2, T.field3) =
(select S.value1, S.value2, S.value3
from srcTable S
where S.key = T.Key);
I believe the correlated subquery can be as complicated as you like (including using CTE. etc). It just has to project the right number (and type) of values.