游标的使用

DECLARE cursor_name CURSOR FOR select_statement;
OPEN cursor_name;
FETCH cursor_name INTO var_name [, var_name] ...
CLOSE cursor_name
declare continue handler FOR SQLSTATE '02000' SET done = 1;  -- done变量需要先声明 declare done int;
示例1：
open cur_test;  
repeat  
    fetch cur_test into name, pass;  
    select concat_ws(',',result,name,pass) into result;  
until done end repeat;  
close cur_test; 

========嵌套游标或多次循环某个游标===========
declare done1 int;
delcare done2 int;
declare CONTINUE HANDLER for not found set done1 = 1;  
begin
delcare xxCur cursor for ...;
set done1=0;
open xxCur;
repeat1:repeat
  fetch xx into ...;
  if (done1=1) then
    leave repeat1;
  end if;
   begin
     declare xx2Cur cursor for ...;
      declare CONTINUE HANDLER for not found set done2 = 1;  
      set done2=0;
      open xx2Cur;
      repeat2:repeat
            fetch xx2 into ...;
            if (done2=1) then
                  leave repeat2;
            end if;
            ...
            
      until (done2=1) end repeat;
      close xx2Cur;
   end;
until (done1=1) end repeat;
close xxCur;
end;

---

通过视图（或临时表）实现动态游标

其实，可以在任意处用begin end把游标套起来就可以随时声明，尤其是嵌套游标的时候

declare cur_temp cursor for select v.* from view_temp_20150701 v;
set v_sql = 'create view view_temp_20150701 as select t.id from t_user t';
set @v_sql = v_sql;
prepare statement from @v_sql;
execute statement;
deallocate prepare statement;