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https://issues.apache.org/jira/browse/PHOENIX-6?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15576121#comment-15576121
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Cameron Hatfield commented on PHOENIX-6:
----------------------------------------

Here is what MSSQL does to handle not having to repeat the actual values 
(though the clause is still repeated), as well as how it supports multiple 
values for the same merge:
{code:sql}
MERGE INTO Sales.SalesReason AS Target  
  USING (VALUES ('Recommendation','Other'), ('Review', 'Marketing'), 
('Internet', 'Promotion'))  
       AS Source (NewName, NewReasonType)  
  ON Target.Name = Source.NewName  
WHEN MATCHED THEN  
  UPDATE SET ReasonType = Source.NewReasonType  
WHEN NOT MATCHED BY TARGET THEN  
  INSERT (Name, ReasonType) VALUES (NewName, NewReasonType)
{code}

> Support ON DUPLICATE KEY construct
> ----------------------------------
>
>                 Key: PHOENIX-6
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-6
>             Project: Phoenix
>          Issue Type: New Feature
>            Reporter: James Taylor
>            Assignee: James Taylor
>             Fix For: 4.9.0
>
>         Attachments: PHOENIX-6_wip1.patch
>
>
> To support inserting a new row only if it doesn't already exist, we should 
> support the "on duplicate key" construct for UPSERT. With this construct, the 
> UPSERT VALUES statement would run atomically and would thus require a read 
> before write which would obviously have a negative impact on performance. For 
> an example of similar syntax , see MySQL documentation at 
> http://dev.mysql.com/doc/refman/5.7/en/insert-on-duplicate.html
> See this discussion for more detail: 
> https://groups.google.com/d/msg/phoenix-hbase-user/Bof-TLrbTGg/68bnc8ZcWe0J. 
> A related discussion is on PHOENIX-2909.
> Initially we'd support the following:
> # This would prevent the setting of VAL to 0 if the row already exists:
> {code}
> UPSERT INTO T (PK, VAL) VALUES ('a',0) 
> ON DUPLICATE KEY IGNORE;
> {code}
> # This would increment the valueS of COUNTER1 and COUNTER2 if the row already 
> exists and otherwise initialize them to 0:
> {code}
> UPSERT INTO T (PK, COUNTER1, COUNTER2) VALUES ('a',0,0) 
> ON DUPLICATE KEY UPDATE COUNTER1 = COUNTER1 + 1, COUNTER2 = COUNTER2 + 1;
> {code}
> So the general form is:
> {code}
> UPSERT ... VALUES ... [ ON DUPLICATE KEY [IGNORE | UPDATE 
> <column>=<expression>, ...] ]
> {code}
> The following restrictions will apply:
> - The <column> may not be part of the primary key constraint - only KeyValue 
> columns will be allowed.
> To handle the maintenance of immutable indexes, we'll need to push the 
> maintenance to the server side.
> This is because the mutations for indexes on immutable tables are calculated 
> on the client-side, while this new syntax would potentially modify the value 
> on the server-side.



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