Sql 比较两组数据

非常抱歉，如果已经以某种方式回答了这个问题。我查遍了，弄不清楚

我需要在postgresql中找到一种方法来比较每周的数据。所有数据都存在于同一个表中，并具有周数列。数据不会总是完全重叠，但我需要在组内比较数据

假设以下是数据集：

Week 2
+--------+--------+------+---------+-------+
| group  |   num  | color|  ID     | week #|
+--------+--------+------+---------+-------+
|    a   |    1   | red  | a1red   |  2    |
|    a   |    2   | blue | a2blue  |  2    |
|    b   |    3   | blue | b3blue  |  2    |
|    c   |    7   | black| c7black |  2    |
|    d   |    8   | black| d8black |  2    |
|    d   |    9   | red  | d9red   |  2    |
|    d   |    10  | gray | d10gray |  2    |
+--------+--------+------+---------+-------+

Week 3
+--------+--------+------+---------+-------+
| group  |   num  | color|  ID     | week #|
+--------+--------+------+---------+-------+
|    a   |    1   | red  | a1red   |   3   |
|    a   |    2   | green| a2green |   3   |
|    b   |    3   | blue | b3blue  |   3   |
|    b   |    5   | green| b5green |   3   |
|    c   |    7   | black| c7black |   3   |
|    e   |    11  | blue | d11blue |   3   |
|    e   |    12  | other| d12other|   3   |
|    e   |    14  | brown| d14brown|   3   |
+--------+--------+------+---------+-------+

每行都有一个由组、编号和颜色值组成的ID

我需要查询以获取第3周中的所有组，然后获取第2周中存在的第3周中的任何组：

组中已更改的标志ID，如组A中的标志ID

标记是否向组中添加或删除了任何ID，如在组B中

有一个功能很好，但不是必需的，那就是对第2周中不存在的组进行第3周与第1周的比较

我曾想过尝试将这两周划分为两周，并使用intercept/except来获得结果，但我无法完全理解如何才能使其正常工作。任何提示都将不胜感激。

在两（已知）周内，您可以执行以下操作：

select coalesce(w1.group_nr, w2.group_nr) as group_nr, 
       coalesce(w1.num, w2.num) as num, 
       case 
         when w1.group_nr is null then 'missing in first week'
         when w2.group_nr is null then 'missing in second week'
         when (w1.color, w1.id) is distinct from (w2.color, w2.id) then 'data has changed'
         else 'no change'
       end as status,
       case
          when 
                 w1.group_nr is not null 
             and w2.group_nr is not null 
             and w1.color is distinct from w2.color then 'color is different'
       end as color_change,
       case 
          when 
                 w1.group_nr is not null 
             and w2.group_nr is not null 
             and w1.id is distinct from w2.id then 'id is different'
       end as id_change
from (
  select group_nr, num, color, id, hstore
  from data
  where week = 2
) as w1
  full outer join (
  select group_nr, num, color, id
    from data
    where week = 3
  ) w2 on (w1.group_nr, w1.num) = (w2.group_nr, w2.num)

获取已更改的属性有点笨拙。如果您可以使用文本表示，则可以使用

hstore

扩展来显示差异：

select coalesce(w1.group_nr, w2.group_nr) as group_nr, 
       coalesce(w1.num, w2.num) as num, 
       case 
         when w1.group_nr is null then 'missing in first week'
         when w2.group_nr is null then 'missing in second week'
         when (w1.color, w1.id) is distinct from (w2.color, w2.id) then 'data has changed'
         else 'no change'
       end as status,
       w2.attributes - w1.attributes as changed_attributes
from (
  select group_nr, num, color, id, hstore(data) - 'week'::text as attributes
  from data
  where week = 2
) as w1
  full outer join (
  select group_nr, num, color, id, hstore(data) - 'week'::text as attributes
    from data
    where week = 3
  ) w2 on (w1.group_nr, w1.num) = (w2.group_nr, w2.num);

---

表中隐藏的周数在哪里？它只是另一列。更新了表格来澄清这一点。啊！非常感谢你。在你规划好基本的思维过程之后，一切都很顺利，现在运行得很好。