Usage
MERGE INTO TABLE_NAME USING table_reference ON (condition) WHEN MATCHED THEN UPDATE SET column1 = value1 WHEN NOT MATCHED THEN INSERT (column1 ) VALUES (value1 [, value2 ...Right join is employed over the Target (the INTO table) and the Source (the USING table / view / sub-query). That is:
- rows present in the Source but missing from the Target do run the action > specifically the NOT MATCHED action
- rows missing from the Source and present in Target are ignored > no action is performed on the Target.
If multiple Source rows match a given Target row, an error is mandated by SQL:2003 standards. You cannot update a Target row multiple times with a MERGE statement
Read more about this topic: Merge (SQL)
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