Redshift 中的嵌套 While 循环

Question

我的Table_1看起来像这样

Parent_Id   Child_Id    Product Prod_count
1000          1            A    1
1000          2          A+B    1
1000          3            A    1
1000          4          B+C    1
2000          1            A    1
2000          2          B+C    1
2000          3            C    1
2000          4            D    1

我正在尝试在此过程中进行嵌套循环，循环基于 Parent_Id，每个父项都有不同的子项，因此也必须读取每一行。

我试过了

create or replace procedure sp_dummy(IN var1 int, IN var2 int, IN var3 int) as $$

Begin

create temp table find_id as(  
      select distinct parent_id,row_number() over(order by 1) as rw_num
      from table_1
);


declare 
  tot_cnt int := (select count(distinct parent_id) from find_id );
  init_loop int := 1;
  in_init_loop int := 1;
  in_tot_init_loop int;
  v_parent_id int;

Begin
  While init_loop <= tot_cnt    
  Loop
  Raise info 'init_loop = %', Init_loop;  
  Execute 'Select parent_id into ' || v_parent_id  || ' from find_id where rw_num = ' || Init_loop;
  Raise info 'v_patient_id = %', v_patient_id;
  
  Execute 'Select Count(*) into ' || in_tot_init_loop  || ' from Table_1 where Parent_Id = ' || v_parent_id;
  
  While in_init_loop <= in_tot_init_loop
  Loop
  Raise info 'in_init_loop = %', in_init_loop;
  in_init_loop = in_init_loop + 1
  End loop;
  
  init_loop = init_loop + 1;
  end loop;     
  
End; 
End;
$$ language plpgsql;

尝试此操作时出现错误无法执行空查询字符串 我放弃了尝试理解这个错误！ :(

Answer 1

这一行似乎有问题：

Execute 'Select parent_id into ' || v_parent_id  || ' from find_id where rw_num = ' || Init_loop;

v_parent_id是空的，所以会翻译成：

Select parent_id into NULL from find_id where rw_num = 1;

我想你真的想写：

SELECT INTO v_parent_id
  parent_id
FROM find_id
WHERE rw_num = Init_loop;

是的，您实际上可以 将 SQL 放在行内 ，而不必将其作为字符串传递给 EXECUTE。看看 Structure of PL/pgSQL - Amazon Redshift.

中的示例

Redshift 中的嵌套 While 循环

Nested While Loop in Redshift

stored-procedures

amazon-web-services

amazon-redshift