UPSERT操作在表中更新或插入一行,这取决于表中是否已经有与数据匹配的行:
if table t has a row exists that has key X:
update t set mystuff... where mykey=X
else
insert into t mystuff...
既然Oracle没有特定的UPSERT语句,那么最好的方法是什么呢?
UPSERT操作在表中更新或插入一行,这取决于表中是否已经有与数据匹配的行:
if table t has a row exists that has key X:
update t set mystuff... where mykey=X
else
insert into t mystuff...
既然Oracle没有特定的UPSERT语句,那么最好的方法是什么呢?
当前回答
我想要Grommit的答案,除了它需要欺骗的值。我在可能出现一次的地方找到了解决方案:http://forums.devshed.com/showpost.php?p=1182653&postcount=2
MERGE INTO KBS.NUFUS_MUHTARLIK B
USING (
SELECT '028-01' CILT, '25' SAYFA, '6' KUTUK, '46603404838' MERNIS_NO
FROM DUAL
) E
ON (B.MERNIS_NO = E.MERNIS_NO)
WHEN MATCHED THEN
UPDATE SET B.CILT = E.CILT, B.SAYFA = E.SAYFA, B.KUTUK = E.KUTUK
WHEN NOT MATCHED THEN
INSERT ( CILT, SAYFA, KUTUK, MERNIS_NO)
VALUES (E.CILT, E.SAYFA, E.KUTUK, E.MERNIS_NO);
其他回答
上面在PL/SQL中的双重示例很棒,因为我想做一些类似的事情,但我想在客户端……所以这里是SQL我用来发送一个类似的语句直接从一些c#
MERGE INTO Employee USING dual ON ( "id"=2097153 )
WHEN MATCHED THEN UPDATE SET "last"="smith" , "name"="john"
WHEN NOT MATCHED THEN INSERT ("id","last","name")
VALUES ( 2097153,"smith", "john" )
然而,从c#的角度来看,这比执行更新和查看受影响的行是否为0以及如果为0则执行插入要慢。
没有异常检查的另一种方法:
UPDATE tablename
SET val1 = in_val1,
val2 = in_val2
WHERE val3 = in_val3;
IF ( sql%rowcount = 0 )
THEN
INSERT INTO tablename
VALUES (in_val1, in_val2, in_val3);
END IF;
正如Tim Sylvester的评论所指出的那样,到目前为止给出的答案在并发访问面前都是不安全的,并且在竞争的情况下会引发异常。为了解决这个问题,必须将插入/更新组合包装在某种循环语句中,以便在出现异常时重新执行整个操作。
举个例子,下面是Grommit的代码如何被包装在一个循环中,以使其在并发运行时安全:
PROCEDURE MyProc (
...
) IS
BEGIN
LOOP
BEGIN
MERGE INTO Employee USING dual ON ( "id"=2097153 )
WHEN MATCHED THEN UPDATE SET "last"="smith" , "name"="john"
WHEN NOT MATCHED THEN INSERT ("id","last","name")
VALUES ( 2097153,"smith", "john" );
EXIT; -- success? -> exit loop
EXCEPTION
WHEN NO_DATA_FOUND THEN -- the entry was concurrently deleted
NULL; -- exception? -> no op, i.e. continue looping
WHEN DUP_VAL_ON_INDEX THEN -- an entry was concurrently inserted
NULL; -- exception? -> no op, i.e. continue looping
END;
END LOOP;
END;
注意:在SERIALIZABLE事务模式下,顺便说一句,我不推荐这种模式,你可能会遇到 ORA-08177:不能序列化此事务异常的访问。
MERGE(“老式的方式”)的替代方案:
begin
insert into t (mykey, mystuff)
values ('X', 123);
exception
when dup_val_on_index then
update t
set mystuff = 123
where mykey = 'X';
end;
从http://www.praetoriate.com/oracle_tips_upserts.htm:
在Oracle9i中,UPSERT可以在一条语句中完成这个任务:
INSERT
FIRST WHEN
credit_limit >=100000
THEN INTO
rich_customers
VALUES(cust_id,cust_credit_limit)
INTO customers
ELSE
INTO customers SELECT * FROM new_customers;