ORACLE多表级联更新( MERGE、UPDATE FROM JOIN替代语句)

方法一：MERGE语句的语法

MERGE INTO 表名
USING 表名/视图/子查询 ON 连接条件 --多个条件注意()括起来
WHEN MATCHED THEN  -- 当匹配得上连接条件时
更新、删除操作
WHEN NOT MATCHED THEN  -- 当匹配不上连接条件时
更新、删除、插入操作

示例

MERGE INTO CAI_GRKMX a USING TMP_IMPHD b
ON (a.SPID=b.SPID AND a.PIHAO=b.PIHAO AND instr(b.pihao,a.djbh)>0)
WHEN MATCHED THEN
 UPDATE SET a.HDUID=b.MXUID,a.HDBZ=1;
COMMIT;

来自网上更好的说明

MERGE INTO dept60_bonuses b
USING (
           SELECT employee_id, salary, department_id
           FROM hr.employees
           WHERE department_id = 60
      ) e
ON (b.employee_id = e.employee_id)
-- 当符合关联条件时
WHEN MATCHED THEN
     -- 将奖金为0的员工的奖金调整为其工资的20%
     UPDATE
     SET b.bonus_amt = e.salary * 0.2
     WHERE b.bonus_amt = 0
     -- 删除工资大于7500的员工奖金记录
     DELETE
     WHERE (e.salary > 7500)
-- 当不符合连接条件时
WHEN NOT MATCHED THEN
     -- 将不在部门为60号的，且不在dept60_bonuses表的用工信息插入，并将其奖金设置为其工资的10%
     INSERT
     (b.employee_id, b.bonus_amt)
     VALUES
     (e.employee_id, e.salary * 0.1)
     WHERE (e.salary < 7500)

方法二：作为多表级联更新的另外一种写法

UPDATE
(SELECT a.HDUID,b.MXUID,HDBZ
FROM CAI_GRKMX a
INNER JOIN TMP_IMPHD b ON a.SPID=b.SPID AND a.PIHAO=b.PIHAO AND instr(b.pihao,a.djbh)>0
)
SET HDUID=MXUID,HDBZ=1