DB2 存储过程中游标循环的嵌套使用方法。

DB2 存储过程中有时候会在一个游标循环内部，还有一个游标循环。

第二个游标循环中，也会使用到第一个游标循环中的值作为输入参数，来获取第二个循环结果。

1 游标循环结构是这样的：

FOR txn as curs CURSOR WITH HOLD FOR

    select fields_name from table where condition group by condition order by fields

DO

    FOR conn as
         select fields_name from table where txn.fields_name group by condition order by fields

   DO

         To Do the job in here

        

    END FOR;

END FOR;

在 To Do the job  位置可以 组织返回结果。这样就可以嵌套循环了。

同样在To Do the job  位置还可以加入select into语句。

如下：

       select count(chgpntcd), sum(kwhconsumed), sum(duration) into totalKWHours, totalKWHours, totalKWHours from ntwpt.rechtxnhis；

       set Response = totalKWHours || totalKWHours || totalKWHours;

2 同样的也可以在第一个循环里面并列加入多个二级For循环：

FOR txn as curs CURSOR WITH HOLD FOR

    select fields_name from table where condition group by condition order by fields

DO

   //第一个并列二级循环

    FOR conn as
         select fields_name from table where txn.fields_name group by condition order by fields

   DO

         To Do the job in here

        

    END FOR;

    //第 二个并列二级循环

    FOR conn as
         select fields_name from table where txn.fields_name group by condition order by fields

   DO

         To Do the job in here

        

    END FOR;

END FOR;