oracle merge鍚屾椂鍖呭惈澧炪€佸垹銆佹敼

Posted 2021-01-20

鏍囩锛?a href='http://www.mamicode.com/so/1/%e7%89%a9%e7%90%86' title='鐗╃悊'>鐗╃悊   this   des   with   瑕佹眰   update   acl   while   rac   

鍘熸潵涓€鐩存病娉ㄦ剰锛宮erge鏄彲浠ユ敮鎸乨elete锛屽彧涓嶈繃蹇呴』鐨勬槸on鏉′欢婊¤冻锛屼篃灏辨槸瑕佹眰绯荤粺鏀寔閫昏緫鍒犻櫎锛岃€岄潪鐗╃悊鍒犻櫎銆?/p>

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 clause condition, it is not deleted.