Question

我想做一个像这样的十大过滤器：

SELECT t0."A" AS d0,
  t0."B" AS d1,
  t0."C" AS d2,
  t0."D" AS d3,
  SUM(t0."SA") AS m0,
  SUM(t0."SB") AS m1
FROM "mock_table_1" AS t0
INNER JOIN (                  //the top 10 filter begin here
  SELECT t0."D" AS fd,
    SUM(t0."SD") AS top
  FROM "mock_table_1" AS t0
  GROUP BY t0."D"
  ORDER BY top ASC
  LIMIT 10
) AS p0u1
ON (t0."D" = p0u1.fd)         //the top 10 filter end here
GROUP BY t0."A",
  t0."B",
  t0."C",
  t0."D"
HAVING (SUM(t0."X") <= 100000000)
LIMIT 100

但是自order-by in subquery not avaliable in Monetdb?

以来这不起作用

那么，我该怎么做才能实现这个前n个过滤器？

简化的SQL示例：

SELECT t0."A" AS d0,
  SUM(t0."SA") AS m0
FROM "mock_table_1" AS t0
INNER JOIN (                    //the top 10 filter begin here
  SELECT t0."D" AS fd,
    SUM(t0."SD") AS top_cond
  FROM "mock_table_1" AS t0
  GROUP BY t0."D"
  ORDER BY top_cond ASC
  LIMIT 10
) AS top_filter
ON (t0."D" = top_filter.fd)     //the top 10 filter end here
GROUP BY t0."A"
LIMIT 100

我想在这里做的是从“mock_table_1”查询A和SUM（SA），其中D在前10-D-成员中，而前10-D-成员表示字段D的成员它具有小的SUM（SD）

Answer 1

因此创建函数来执行此操作，返回未受阻碍的（通过子查询限制）表

CREATE FUNCTION my_cheating_function() 
   RETURNS TABLE (fd [data type for fd], top [data type for top])
   RETURN TABLE (
        SELECT 
           t0."D" AS fd,
           SUM(t0."SD") AS top
        FROM 
           "mock_table_1" AS t0
        GROUP BY 
           t0."D"
        ORDER BY 
           top ASC
        LIMIT 10
   );

然后修改原始查询：

  SELECT t0."A" AS d0,
   t0."B" AS d1,
   t0."C" AS d2,
   t0."D" AS d3,
   SUM(t0."SA") AS m0,
   SUM(t0."SB") AS m1
  FROM 
   "mock_table_1" AS t0
  INNER JOIN 
   my_cheating_function() AS p0u1
  ON 
   (t0."D" = p0u1.fd)        
  GROUP BY 
   t0."A",
   t0."B",
   t0."C",
   t0."D"
  HAVING (SUM(t0."X") <= 100000000)
  LIMIT 100;

这很可能也可以通过在该子查询上创建视图并以与上述类似的方式加入视图来完成。仅供参考创建该视图，请执行以下操作：

CREATE VIEW my_cheating_view AS
    SELECT 
       t0."D" AS fd,
       SUM(t0."SD") AS top
    FROM 
       "mock_table_1" AS t0
    GROUP BY 
       t0."D"
    ORDER BY 
       top ASC
    LIMIT 10;

如何在Monetdb中实现前n个过滤器？

1 个答案: