MERGE语句是Oracle9i新增的语法，用来合并UPDATE和INSERT语句。 通过MERGE语句，根据一张表或多表联合查询的连接条件对另外一张表进行查询，连接条件匹配上的进行UPDATE，无法匹配的执行INSERT。这个语法仅需要一次全表扫描就完成了全部工作，执行效率要高于INSERT＋UPDATE。通过这个MERGE你能够在一个SQL语句中对一个表同时执行INSERT和UPDATE操作. 在 Oracle 10g中MERGE有一些新特性，后面我会介绍这些新特征。先看看MERGE语法如下：
MERGE INTO DM.TM_WGG_SYSVLRUSER_HR DM USING
(
SELECT DATE_CD,
HR_CD,
DATE_HR,
DECODE(GROUPING(CITY_ID), 1, 9999, CITY_ID) AS CITY_ID,
DECODE(GROUPING(SYSTEM_ID), 1, -9999, SYSTEM_ID) AS SYSTEM_ID,
SUM(GSM_REG_USERCNT) AS GSM_REG_USERCNT,
SUM(TD_REG_USERCNT) AS TD_REG_USERCNT,
SUM(TD_REG_USERRAT) AS TD_REG_USERRAT,
SUM(GSM_POWERON_USERCNT) AS GSM_POWERON_USERCNT,
SUM(TD_POWERON_USERCNT) AS TD_POWERON_USERCNT,
SUM(TD_POWERON_USERRAT) AS TD_POWERON_USERRAT
FROM DM.TM_WGG_SYSVLRUSER_HR
GROUP BY DATE_HR, DATE_CD, HR_CD, ROLLUP(SYSTEM_ID),ROLLUP(CITY_ID)
) TMP
ON
(
DM.DATE_CD = TMP.DATE_CD
AND DM.HR_CD = TMP.HR_CD
AND DM.CITY_ID = TMP.CITY_ID
AND DM.SYSTEM_ID = TMP.SYSTEM_ID
)
WHEN MATCHED THEN UPDATE SET
DM.GSM_REG_USERCNT = TMP.GSM_REG_USERCNT,
DM.TD_REG_USERCNT = TMP.TD_REG_USERCNT,
DM.TD_REG_USERRAT = TMP.TD_REG_USERRAT,
DM.GSM_POWERON_USERCNT = TMP.GSM_POWERON_USERCNT,
DM.TD_POWERON_USERCNT = TMP.TD_POWERON_USERCNT,
DM.TD_POWERON_USERRAT = TMP.TD_POWERON_USERRAT,
DM.DATE_HR = TMP.DATE_HR
WHEN NOT MATCHED THEN
INSERT
(
DM.DATE_CD,
DM.HR_CD,
DM.DATE_HR,
DM.CITY_ID,
DM.SYSTEM_ID,
DM.GSM_REG_USERCNT,
DM.TD_REG_USERCNT,
DM.TD_REG_USERRAT,
DM.GSM_POWERON_USERCNT,
DM.TD_POWERON_USERCNT,
DM.TD_POWERON_USERRAT
)
VALUES
(
TMP.DATE_CD,
TMP.HR_CD,
TMP.DATE_HR,
TMP.CITY_ID,
TMP.SYSTEM_ID,
TMP.GSM_REG_USERCNT,
TMP.TD_REG_USERCNT,
TMP.TD_REG_USERRAT,
TMP.GSM_POWERON_USERCNT,
TMP.TD_POWERON_USERCNT,
TMP.TD_POWERON_USERRAT
(
SELECT DATE_CD,
HR_CD,
DATE_HR,
DECODE(GROUPING(CITY_ID), 1, 9999, CITY_ID) AS CITY_ID,
DECODE(GROUPING(SYSTEM_ID), 1, -9999, SYSTEM_ID) AS SYSTEM_ID,
SUM(GSM_REG_USERCNT) AS GSM_REG_USERCNT,
SUM(TD_REG_USERCNT) AS TD_REG_USERCNT,
SUM(TD_REG_USERRAT) AS TD_REG_USERRAT,
SUM(GSM_POWERON_USERCNT) AS GSM_POWERON_USERCNT,
SUM(TD_POWERON_USERCNT) AS TD_POWERON_USERCNT,
SUM(TD_POWERON_USERRAT) AS TD_POWERON_USERRAT
FROM DM.TM_WGG_SYSVLRUSER_HR
GROUP BY DATE_HR, DATE_CD, HR_CD, ROLLUP(SYSTEM_ID),ROLLUP(CITY_ID)
) TMP
ON
(
DM.DATE_CD = TMP.DATE_CD
AND DM.HR_CD = TMP.HR_CD
AND DM.CITY_ID = TMP.CITY_ID
AND DM.SYSTEM_ID = TMP.SYSTEM_ID
)
WHEN MATCHED THEN UPDATE SET
DM.GSM_REG_USERCNT = TMP.GSM_REG_USERCNT,
DM.TD_REG_USERCNT = TMP.TD_REG_USERCNT,
DM.TD_REG_USERRAT = TMP.TD_REG_USERRAT,
DM.GSM_POWERON_USERCNT = TMP.GSM_POWERON_USERCNT,
DM.TD_POWERON_USERCNT = TMP.TD_POWERON_USERCNT,
DM.TD_POWERON_USERRAT = TMP.TD_POWERON_USERRAT,
DM.DATE_HR = TMP.DATE_HR
WHEN NOT MATCHED THEN
INSERT
(
DM.DATE_CD,
DM.HR_CD,
DM.DATE_HR,
DM.CITY_ID,
DM.SYSTEM_ID,
DM.GSM_REG_USERCNT,
DM.TD_REG_USERCNT,
DM.TD_REG_USERRAT,
DM.GSM_POWERON_USERCNT,
DM.TD_POWERON_USERCNT,
DM.TD_POWERON_USERRAT
)
VALUES
(
TMP.DATE_CD,
TMP.HR_CD,
TMP.DATE_HR,
TMP.CITY_ID,
TMP.SYSTEM_ID,
TMP.GSM_REG_USERCNT,
TMP.TD_REG_USERCNT,
TMP.TD_REG_USERRAT,
TMP.GSM_POWERON_USERCNT,
TMP.TD_POWERON_USERCNT,
TMP.TD_POWERON_USERRAT
);
在ORACLE 10i中，MERGE有如下一些新特性。
1、UPDATE或INSERT子句是可选的
假如某个系统中，有个订单表，现在要求新增订单的记录都要反应到订单历史表ORDER_HISTORY中，我们可以如下写脚本
MERGE INTO ORDER_HISTORY H USING
(
SELECT ORDER_ID ,--订单编号
CUSTOMER_ID ,--客户编号
EMPLOYEE_ID ,--员工编号
ORDER_DATE ,--订购日期；
REQUIRED_DATE ,--预计到达日期
SHIPPED_DATE ,--发货日期
SHIPPER ,--运货商
FREIGHT ,--运费
SHIP_NAM ,--货主姓名；
SHIP_ADDRESS ,--货主地址
SHIP_CITY ,--货主所在城市；
SHIP_REGION ,--货主所在地区；
SHIP_POSTALCODE ,--货主邮编
SHIP_COUNTRY --货主所在国家
FROM ORDER_DTL
WHERE TO_CHAR(ODER_DATE, 'YYYY-MM-DD') = '20110530'
) O
ON
(
O.ORDER_ID = H.ORDER_ID
)
WHEN NOT MATCHED THEN INSERT
(
H.ORDER_ID ,
H.CUSTOMER_ID ,
H.EMPLOYEE_ID ,
H.ORDER_DATE ,
H.REQUIRED_DATE ,
H.SHIPPED_DATE ,
H.SHIPPER ,
H.FREIGHT ,
H.SHIP_NAM ,
H.SHIP_ADDRESS ,
H.SHIP_CITY ,
H.SHIP_REGION ,
H.SHIP_POSTALCODE ,
H.SHIP_COUNTRY
)
VALUES
(
O.ORDER_ID ,
O.CUSTOMER_ID ,
O.EMPLOYEE_ID ,
O.ORDER_DATE ,
O.REQUIRED_DATE ,
O.SHIPPED_DATE ,
O.SHIPPER ,
O.FREIGHT ,
O.SHIP_NAM ,
O.SHIP_ADDRESS ,
O.SHIP_CITY ,
O.SHIP_REGION ,
O.SHIP_POSTALCODE ,
O.SHIP_COUNTRY
(
SELECT ORDER_ID ,--订单编号
CUSTOMER_ID ,--客户编号
EMPLOYEE_ID ,--员工编号
ORDER_DATE ,--订购日期；
REQUIRED_DATE ,--预计到达日期
SHIPPED_DATE ,--发货日期
SHIPPER ,--运货商
FREIGHT ,--运费
SHIP_NAM ,--货主姓名；
SHIP_ADDRESS ,--货主地址
SHIP_CITY ,--货主所在城市；
SHIP_REGION ,--货主所在地区；
SHIP_POSTALCODE ,--货主邮编
SHIP_COUNTRY --货主所在国家
FROM ORDER_DTL
WHERE TO_CHAR(ODER_DATE, 'YYYY-MM-DD') = '20110530'
) O
ON
(
O.ORDER_ID = H.ORDER_ID
)
WHEN NOT MATCHED THEN INSERT
(
H.ORDER_ID ,
H.CUSTOMER_ID ,
H.EMPLOYEE_ID ,
H.ORDER_DATE ,
H.REQUIRED_DATE ,
H.SHIPPED_DATE ,
H.SHIPPER ,
H.FREIGHT ,
H.SHIP_NAM ,
H.SHIP_ADDRESS ,
H.SHIP_CITY ,
H.SHIP_REGION ,
H.SHIP_POSTALCODE ,
H.SHIP_COUNTRY
)
VALUES
(
O.ORDER_ID ,
O.CUSTOMER_ID ,
O.EMPLOYEE_ID ,
O.ORDER_DATE ,
O.REQUIRED_DATE ,
O.SHIPPED_DATE ,
O.SHIPPER ,
O.FREIGHT ,
O.SHIP_NAM ,
O.SHIP_ADDRESS ,
O.SHIP_CITY ,
O.SHIP_REGION ,
O.SHIP_POSTALCODE ,
O.SHIP_COUNTRY
);
从上可以看出，MATCHED 或NOT MATCHED是可选的。不必非得
WHEN NOT MATCHED THEN UPDATE SET
.....
WHEN MATCHED THEN INSERT
2、UPDATE和INSERT子句可以加WHERE子句
现在由于需求改变，我们仅仅需要把员工1001的订单数据同步到订单历史记录表
MERGE INTO ORDER_HISTORY H USING
(
SELECT ORDER_ID ,--订单编号
CUSTOMER_ID ,--客户编号
EMPLOYEE_ID ,--员工编号
ORDER_DATE ,--订购日期；
REQUIRED_DATE ,--预计到达日期
SHIPPED_DATE ,--发货日期
SHIPPER ,--运货商
FREIGHT ,--运费
SHIP_NAM ,--货主姓名；
SHIP_ADDRESS ,--货主地址
SHIP_CITY ,--货主所在城市；
SHIP_REGION ,--货主所在地区；
SHIP_POSTALCODE ,--货主邮编
SHIP_COUNTRY --货主所在国家
FROM ORDER_DTL
) O
ON
(
O.ORDER_ID = H.ORDER_ID
)
WHEN MATCHED THEN UPDATE SET
H.CUSTOMER_ID = O.CUSTOMER_ID ,
H.EMPLOYEE_ID = O.EMPLOYEE_ID ,
H.ORDER_DATE = O.ORDER_DATE ,
H.REQUIRED_DATE = O.REQUIRED_DATE ,
H.SHIPPED_DATE = O.SHIPPED_DATE ,
H.SHIPPER = O.SHIPPER ,
H.FREIGHT = O.FREIGHT ,
H.SHIP_NAM = O.SHIP_NAM ,
H.SHIP_ADDRESS = O.SHIP_ADDRESS ,
H.SHIP_CITY = O.SHIP_CITY ,
H.SHIP_REGION = O.SHIP_REGION ,
H.SHIP_POSTALCODE = O.SHIP_POSTALCODE ,
H.SHIP_COUNTRY = O.SHIP_COUNTRY
WHERE O.EMPLOYEE_ID = 1001
WHEN NOT MATCHED THEN INSERT
(
H.ORDER_ID ,
H.CUSTOMER_ID ,
H.EMPLOYEE_ID ,
H.ORDER_DATE ,
H.REQUIRED_DATE ,
H.SHIPPED_DATE ,
H.SHIPPER ,
H.FREIGHT ,
H.SHIP_NAM ,
H.SHIP_ADDRESS ,
H.SHIP_CITY ,
H.SHIP_REGION ,
H.SHIP_POSTALCODE ,
H.SHIP_COUNTRY
)
VALUES
(
O.ORDER_ID ,
O.CUSTOMER_ID ,
O.EMPLOYEE_ID ,
O.ORDER_DATE ,
O.REQUIRED_DATE ,
O.SHIPPED_DATE ,
O.SHIPPER ,
O.FREIGHT ,
O.SHIP_NAM ,
O.SHIP_ADDRESS ,
O.SHIP_CITY ,
O.SHIP_REGION ,
O.SHIP_POSTALCODE ,
O.SHIP_COUNTRY
)
(
SELECT ORDER_ID ,--订单编号
CUSTOMER_ID ,--客户编号
EMPLOYEE_ID ,--员工编号
ORDER_DATE ,--订购日期；
REQUIRED_DATE ,--预计到达日期
SHIPPED_DATE ,--发货日期
SHIPPER ,--运货商
FREIGHT ,--运费
SHIP_NAM ,--货主姓名；
SHIP_ADDRESS ,--货主地址
SHIP_CITY ,--货主所在城市；
SHIP_REGION ,--货主所在地区；
SHIP_POSTALCODE ,--货主邮编
SHIP_COUNTRY --货主所在国家
FROM ORDER_DTL
) O
ON
(
O.ORDER_ID = H.ORDER_ID
)
WHEN MATCHED THEN UPDATE SET
H.CUSTOMER_ID = O.CUSTOMER_ID ,
H.EMPLOYEE_ID = O.EMPLOYEE_ID ,
H.ORDER_DATE = O.ORDER_DATE ,
H.REQUIRED_DATE = O.REQUIRED_DATE ,
H.SHIPPED_DATE = O.SHIPPED_DATE ,
H.SHIPPER = O.SHIPPER ,
H.FREIGHT = O.FREIGHT ,
H.SHIP_NAM = O.SHIP_NAM ,
H.SHIP_ADDRESS = O.SHIP_ADDRESS ,
H.SHIP_CITY = O.SHIP_CITY ,
H.SHIP_REGION = O.SHIP_REGION ,
H.SHIP_POSTALCODE = O.SHIP_POSTALCODE ,
H.SHIP_COUNTRY = O.SHIP_COUNTRY
WHERE O.EMPLOYEE_ID = 1001
WHEN NOT MATCHED THEN INSERT
(
H.ORDER_ID ,
H.CUSTOMER_ID ,
H.EMPLOYEE_ID ,
H.ORDER_DATE ,
H.REQUIRED_DATE ,
H.SHIPPED_DATE ,
H.SHIPPER ,
H.FREIGHT ,
H.SHIP_NAM ,
H.SHIP_ADDRESS ,
H.SHIP_CITY ,
H.SHIP_REGION ,
H.SHIP_POSTALCODE ,
H.SHIP_COUNTRY
)
VALUES
(
O.ORDER_ID ,
O.CUSTOMER_ID ,
O.EMPLOYEE_ID ,
O.ORDER_DATE ,
O.REQUIRED_DATE ,
O.SHIPPED_DATE ,
O.SHIPPER ,
O.FREIGHT ,
O.SHIP_NAM ,
O.SHIP_ADDRESS ,
O.SHIP_CITY ,
O.SHIP_REGION ,
O.SHIP_POSTALCODE ,
O.SHIP_COUNTRY
)
WHERE O.EMPLOYEE_ID = 1001
3、在ON条件中使用常量过滤谓词来insert所有的行到目标表中,不需要连接源表和目标表
4、UPDATE子句后面可以跟DELETE子句来去除一些不需要的行
