理解MySQL中的游标（Cursor）操作

cursor

1.  declare

    eg: declare c1 cursor for ....(sql select salary from employees;) 

    declare <游标名> cursor for <select语句>;

2.  open

    eg: open c1;

    open <游标名>;

3.  operation
    eg: loop
            fetch c1 into a;
        end loop;

    fetch <游标名> into <变量1>,<变量2>...

    

4.  close

    eg: close c1;

    close <游标名>;

 

举例说明：

delimiter //
create procedure p_11()
begin
 declare c_total float(8,2);
 declare c_name varchar(20);
 declare c_salary float(8,2);
 declare c_comm float(3,2);
 declare c1 cursor for select name, salary, comm from employees;
 declare exit handler for not found
 begin  close c1; end;
 open c1;
 loop 
   fetch c1 into c_name, c_salary, c_comm;
   select ( c_salary * ifnull(c_comm,0) + c_salary ) into c_total from dual;
   update salary set salary=c_total where name=c_name;
 end loop;
 close c1;
end
//
delimiter ;