MERGE语句合并两个表之间的数据。使用双 允许我们使用此命令。请注意，这没有针对并发访问进行保护。

create or replace
procedure ups(xa number)
as
begin
    merge into mergetest m using dual on (a = xa)
         when not matched then insert (a,b) values (xa,1)
             when matched then update set b = b+1;
end ups;
/
drop table mergetest;
create table mergetest(a number, b number);
call ups(10);
call ups(10);
call ups(20);
select * from mergetest;

A                      B
---------------------- ----------------------
10                     2
20                     1

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;

MERGE语句合并两个表之间的数据。使用双 允许我们使用此命令。请注意，这没有针对并发访问进行保护。

create or replace
procedure ups(xa number)
as
begin
    merge into mergetest m using dual on (a = xa)
         when not matched then insert (a,b) values (xa,1)
             when matched then update set b = b+1;
end ups;
/
drop table mergetest;
create table mergetest(a number, b number);
call ups(10);
call ups(10);
call ups(20);
select * from mergetest;

A                      B
---------------------- ----------------------
10                     2
20                     1

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;

如果不存在，请插入 更新:

    
INSERT INTO mytable (id1, t1) 
  SELECT 11, 'x1' FROM DUAL 
  WHERE NOT EXISTS (SELECT id1 FROM mytble WHERE id1 = 11); 

UPDATE mytable SET t1 = 'x1' WHERE id1 = 11;

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。