Each row in the TRANS_SUMMARY table contains details of one product.

　　Each row in the TRANS_MONTHLY table contains transaction details either for new products or for

　　updates to existing products.

　　There is a monthly requirement to:

　　1.Insert TRANS_MONTHLY rows for new products to the TRANS_SUMMARY table

　　2.Update the TRANS_SUMMARY table when a TRANS_MONTHLY row refers to an existing product.

　　Which two can be used to do this?

　　A)INSERT INTO .. SELECT FROM ..

　　B)a called procedure.

　　C)an Oracle loader type external table.

　　D)the MERGE command.

　　E)CREATE TABLE AS SELECT (CTAS)

　　Answer: BD

　　题译：

　　每月需要：

　　1 将 TRANS_MONTHLY 表中的新产品的行插入到 TRANS_SUMMARY 汇总表

　　2 对已有的产品进行更新

　　MERGE INTO T T1

　　USING (SELECT '1001' AS a,2 AS b FROM dual) T2

　　ON ( T1.a=T2.a)

　　WHEN MATCHED THEN

　　UPDATE SET T1.b = T2.b

　　WHEN NOT MATCHED THEN

　　INSERT (a,b) VALUES(T2.a,T2.b);