oracle中merge into..using..on..when..when..用法

zhufeng518

原文：oracle中merge into..using..on..when..when..用法
　　语法：
　　Sql代码  http://azrael6619.iteye.com/images/icon_star.png

• 　　MERGE INTO [your table-name] [rename your table here]
  
• 
  
• 　　USING ( [write your query here] )[rename your query-sql and using just like a table]
  
• 
  
• 　　ON ([conditional expression here] AND [...]...)
  
• 
  
• 　　WHEN MATHED THEN [here you can execute some update sql or something else ]
  
• 
  
• 　　WHEN NOT MATHED THEN [execute something else here ! ]
  

　　实例：
　　Sql代码  http://azrael6619.iteye.com/images/icon_star.png

• 　　merge into tfa_alarm_act_nms a
  
• 　　using (select FP0,FP1,FP2,FP3,REDEFINE_SEVERITY
  
• 　　from tfa_alarm_status) b
  
• 　　on (a.fp0=b.fp0 and a.fp1=b.fp1 and a.fp2=b.fp2 and a.fp3=b.fp3)
  
• 　　when matched then update set a.redefine_severity=b.redefine_severity
  
• 　　when not matched then insert (a.fp0,a.fp1,a.fp2,a.fp3,a.org_severity,a.redefine_severity,
  
• 　　a.event_time  ,a.int_id)
  
• 　　values (b.fp0,b.fp1,b.fp2,b.fp3,b.REDEFINE_SEVERITY,b.redefine_severity,sysdate,7777778);
  

　　作用：利用表 tfa_alarm_status跟新表tfa_alarm_act_nms 的b.redefine_severity，条件是a.fp0=b.fp0 and a.fp1=b.fp1 and a.fp2=b.fp2 and a.fp3=b.fp3，如果tfa_alarm_act_nms表中没有该条件的数据就插入。