oracle merge into 的用法详解+实例
2010-09-26 08:51
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作用:merge into 解决用B表跟新A表数据,如果A表中没有,则把B表的数据插入A表; 语法: 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----------------------------------------------------------------- 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。 如果你的数据量很大,此sql效率非常高。
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