很多Mysql转达梦的朋友会碰到这个问题,MySQL 插入数据的时候支持ON DUPLICATE KEY UPDATE
对于主键重复的数据可以执行更新而不是报错,目前达梦数据库还未支持这个语法,那应该怎么处理呢?
下面给大家介绍一下,在DM和Oracle中都可以改写为merge语句
--创建测试表,插入数据
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,插入一条记录如果存在就update
INSERT INTO mRowUpdate(id,cnt) VALUES(3, 'SuperMan') ON DUPLICATE KEY UPDATE cnt='SuperMan';
--达梦中需要用merge语句来改写
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;
--查看执行结果
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);
--达梦对于多行数据的改写方法
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
--查看执行结果
SELECT * FROM mRowUpdate;