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https://issues.apache.org/jira/browse/DERBY-6723?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14117220#comment-14117220
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Knut Anders Hatlen commented on DERBY-6723:
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I believe the standard does allow it, but it is currently disabled because of
some technical challenges when the source table is not a base table. There is a
similar request for allowing views as source (DERBY-6656), and it sounds as if
the underlying problem that needs to be solved, is the same for both of these
issues.
> Allow derived table as a source in MERGE statement
> --------------------------------------------------
>
> Key: DERBY-6723
> URL: https://issues.apache.org/jira/browse/DERBY-6723
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 10.11.1.1
> Reporter: Aleksei Kovura
> Priority: Minor
>
> I'm trying to utilize MERGE to do an upsert operation like this:
> MERGE INTO "APP"."ST_KEY_VAL" trg USING (SELECT * FROM (VALUES ('key1',
> 'val1')) as t1 (st_key, st_val)) as src
> ON trg.st_key = src.st_key
> WHEN MATCHED THEN UPDATE SET st_val = src.st_val
> WHEN NOT MATCHED THEN INSERT VALUES (src.st_key, src.st_val)
> ;
> Derby returns an error:
> Error: The source table of a MERGE statement must be a base table or table
> function.
> SQLState: 42XAL
> ErrorCode: 30000
> MERGE is used this way on other databases, unfortunately I can't find whether
> it is standard compliant or not. If this gets implemented, I would use it in
> PreparedStatement, replacing values with "?"-s.
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