I have two tables ALPHA and BETA. I need to update the BETAID to the ALPHAID. The BETAID is currently set to the ALPHADESC so I am joining on this column.
The following update statement works fine in SQL Server:
UPDATE BETA
SET BETAID= A.ALPHAID
FROM TABLE BETA
INNER JOIN ALPHA A
ON BETAID= A.ALPHADESC
So using the lookup table Alpha:-
ALPHAID ALPHADESC
1 First
2 Second
3 Third
This changes the Beta table from:-
BETAID
First
Second
Third
To:-
BETAID
1
2
3
So, the query is simply using a lookup table to replace a description with its corresponding ID, one row at a time. I now need to replicate this query in Oracle. Using the following:-
UPDATE BETA
SET BETAID = (SELECT A.ALPHAID FROM ALPHA A, BETA B
WHERE B.BETAID = A.ALPHADESC);
Results in 'single-row subquery returns more than one row', as expected. How would I rewrite this query for oracle?
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Harish, MAX(A.ALPHAID) sets, all the BETAID's to the highest value in the lookup table, so if I have a table with 1/3 'First', 1/3 'Second' and 1/3 'Third, it sets all the BETAIDs to '3', which is incorrect. I've also tried group by, having count and distinct and none of these update the rows one at a time like the inner join syntax does.
If there are no duplicates then this should work:
UPDATE beta b
SET b.betaid = (SELECT a.alphaid
FROM alpha a
WHERE a.alphadesc = b.betaid)
If there dupes then this will work:
UPDATE beta b
set b.betaid = (SELECT a.alphaid
FROM (SELECT a.alphaid,a.alphadesc
FROM alpha a
GROUP BY a.alphaid,a.alphadesc) a
WHERE a.alphadesc = b.betaid)
yes, you need the exists to ensure only rows with matching values are updated and the max to ensure that you only get one row on the updating subquery, also, the subquery has to be a 'collated' subquery so that it retrieves child records that match the parent. The "and exists ...." can be left out if ou know there is a matching record in alpha for every record in beta.
UPDATE BETA
SET BETAID = (SELECT max(A.ALPHAID) FROM ALPHA A, BETA B
WHERE B.BETAID = A.ALPHADESC)
and exists (select 'x' from alpha a, beta b where b.betaid=a.alphadesc);
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by: mgh_mgharishPosted on 2006-01-29 at 16:22:42ID: 15820108
Hi servantis, try this:
UPDATE BETA
SET BETAID = (SELECT MAX(A.ALPHAID) FROM ALPHA A, BETA B
WHERE B.BETAID = A.ALPHADESC);
---
Harish