Oracle数据库Merge的使用
语法：
         merge into table_name talbe_alias        //目标表
         using(table | view | sub_query) alias      //源表
         on(join condition)                                //合并数据的条件
         when matched then                             //如果条件成立则更新
         update set col1=col_val, col2=co2_val...
         when not matched then                       //如果条件不成立则插入
         insert (column_list) values(column_values);


示例：
         //新建一张表
         create table test1(
          eid number(10),
          name varchar2(20),
          birth date,
          salary number(8,2)
         );




         //向表中插入数据
         insert into test1 values(1001,'张三','20-5月',2300);
         insert into test1 values(1002,'张三','01-6月',3000);

         //查询表中的数据
         select * from test1;


          //新建第二张表，在表中不插入任何数据
          create table test2(
          eid number(10),
          name varchar2(20),
          birth date,
          salary number(8,2)
         );

         //查询第二张表中的数据
         select * from test2;


         //使用merge进行数据合并
         merge into test2
         using test1
         on(test.eid = test2.eid)
         when matched then
          update set name = test1.name, birth = test1.birth, salary = test1.salary
         when not matched then
          insert(eid,name,birth,salary) values(test1.eid, test1.name, test1.birth, test1.salaru);

         select * from test2