oracle merge同時包含增、刪、改
原來一直沒註意,merge是可以支持delete,只不過必須的是on條件滿足,也就是要求系統支持邏輯刪除,而非物理刪除。
Using the DELETE Clause with MERGE Statements
You may want to cleanse tables while populating or updating them. To do this, you may want to consider using the DELETE
clause in a MERGE
statement, as in the following example:
MERGE USING Product_Changes S INTO Products D ON (D.PROD_ID = S.PROD_ID) WHEN MATCHED THEN UPDATE SET D.PROD_LIST_PRICE =S.PROD_NEW_PRICE, D.PROD_STATUS = S.PROD_NEWSTATUS DELETE WHERE(D.PROD_STATUS = "OBSOLETE") WHEN NOT MATCHED THEN INSERT (PROD_ID, PROD_LIST_PRICE, PROD_STATUS) VALUES (S.PROD_ID, S.PROD_NEW_PRICE, S.PROD_NEW_STATUS);
Thus when a row is updated in products
, Oracle checks the delete condition D.PROD_STATUS = "OBSOLETE"
, and deletes the row if the condition yields true.
The DELETE
operation is not as same as that of a complete DELETE
statement. Only the rows from the destination of the MERGE
can be deleted. The only rows that are affected by the DELETE
are the ones that are updated by this MERGE
statement. Thus, although a given row of the destination table meets the delete condition, if it does not join under the ON
oracle merge同時包含增、刪、改