Mysql insert ON DUPLICATE KEY UPDATE在達夢數據庫中如何轉換？

很多Mysql轉達夢的朋友會碰到這個問題，MySQL 插入數據的時候支持ON DUPLICATE KEY UPDATE

對於主鍵重複的數據可以執行更新而不是報錯，目前達夢數據庫還未支持這個語法，那應該怎麼處理呢？

下面給大家介紹一下，在DM和Oracle中都可以改寫爲merge語句

--創建測試表，插入數據
DROP TABLE IF EXISTS mRowUpdate;
CREATE TABLE mRowUpdate (
  id int NOT NULL,
  cnt varchar(255)  NULL,
  PRIMARY KEY (id)
);

INSERT INTO mRowUpdate VALUES (1, 'sss');
INSERT INTO mRowUpdate VALUES (2, 'szh');
INSERT INTO mRowUpdate VALUES (3, '9999');
commit;

--Mysql用法，插入一條記錄如果存在就update
INSERT INTO mRowUpdate(id,cnt) VALUES(3, 'SuperMan') ON DUPLICATE KEY UPDATE cnt='SuperMan';

--達夢中需要用merge語句來改寫
merge into mRowUpdate as t1 USING (select 3 id,'SuperMan' cnt from dual ) as t2
   on t1.id=t2.id  
WHEN MATCHED THEN  
   update  set t1.cnt=t2.cnt
WHEN NOT MATCHED THEN
   INSERT VALUES(3, 'SuperMan');   
commit;

--查看執行結果
select * from mRowUpdate;


--Mysql插入多行

INSERT INTO mRowUpdate(id,cnt) VALUES 
                         ('2','UPDATE') ,
                         ('4','INSERT')
 ON DUPLICATE KEY UPDATE cnt =  VALUES(cnt);


--達夢對於多行數據的改寫方法
MERGE INTO mRowUpdate T1  
USING (SELECT 2 as ID,'UPDATE' as CNT FROM DUAL
UNION ALL 
SELECT '4','INSERT' FROM DUAL) T2 ON (T1.id = T2.id)
WHEN NOT MATCHED THEN INSERT(id, CNT) VALUES
(T2.id, T2.CNT)
WHEN MATCHED THEN UPDATE
SET T1.CNT = T2.CNT

--查看執行結果
SELECT * FROM mRowUpdate;