[英]SQL aggregation using group by of columns one by one
Scenario:设想:
Below is my table.下面是我的桌子。
+-------+-----------+--------+--------+
|col2 |col3 |col4 |col5 |
+-------+-----------+--------+--------+
| 1.0| 2| a| a1|
| 1.0| 1| a| a2|
| 1.0| 2| b| a3|
| 2.0| 1| a| a1|
| 2.0| 1| a| a2|
+-------+-----------+--------+--------+
I need to get the aggregated result as below.我需要获得如下汇总结果。
+-------+-----------+-----------+-----------+-----+
|col2 |col3 | field_name|field_value|count|
+-------+-----------+-----------+-----------+-----+
| 2.0| 1| col3 | 1| 2|
| 1.0| 1| col3 | 1| 1|
| 1.0| 2| col3 | 2| 2|
| 2.0| 1| col4 | a| 2|
| 1.0| 1| col4 | a| 1|
| 1.0| 2| col4 | a| 1|
| 1.0| 2| col4 | b| 1|
| 1.0| 1| col5 | a2| 1|
| 1.0| 2| col5 | a1| 1|
| 1.0| 2| col5 | a3| 1|
| 2.0| 1| col5 | a1| 1|
| 2.0| 1| col5 | a2| 1|
+-------+-----------+-----------+-----------+-----+
Implemented Solution:实施方案:
I implemented the solution by creating three different tables[T1, T2, T3].我通过创建三个不同的表 [T1、T2、T3] 来实现该解决方案。 And then for each table, I created [rowset1, rowset2, rowset3] programmatically to combine all into a single table
然后对于每个表,我以编程方式创建了 [rowset1, rowset2, rowset3] 以将所有这些组合成一个表
select col2, col3, col3, count(*) from calc group by col2, col3;
T1 :
|col2 |col3 |col3 |count|
+-------+-----------+-----------+-----+
| 2.0| 1| 1| 2|
| 1.0| 1| 1| 1|
| 1.0| 2| 2| 2|
+-------+-----------+-----------+-----+
rowset1 = [[2.0,1,col3,1,2,18000], [1.0,1,col3,1,1,18000], [1.0,2,col3,2,2,18000]]
select col2, col3, col4, count(*) from calc group by col2, col3, col4;
T2:
+-------+-----------+--------+-----+
|col2 |col3 |col4 |count|
+-------+-----------+--------+-----+
| 2.0| 1| a| 2|
| 1.0| 1| a| 1|
| 1.0| 2| a| 1|
| 1.0| 2| b| 1|
+-------+-----------+--------+-----+
rowset2 = [[2.0,1,col4,a,2,18000], [1.0,1,col4,a,1,18000], [1.0,2,col4,a,1,18000],[1.0,2,col4,b,1,18000]]
select col2, col3, col5 , count(*) from calc group by col2, col3, col5;
T3:
+-------+-----------+--------+-----+
|col2 |col3 |col5 |count|
+-------+-----------+--------+-----+
| 1.0| 1| a2| 1|
| 1.0| 2| a1| 1|
| 1.0| 2| a3| 1|
| 2.0| 1| a1| 1|
| 2.0| 1| a2| 1|
+-------+-----------+--------+-----+
rowset3 = [1.0,2,col5,b,1,18000], [1.0,1,col5,a2,1,18000], [1.0,2,col5,a1,1,18000], [1.0,2,col5,a3,1,18000], [2.0,1,col5,a1,1,18000], [2.0,1,col5,a2,1,18000]]
Problem :问题:
How can I achieve the same in SQL without an overhead of creating rowset1,2,3 and combining it into a single table?如何在没有创建 rowset1,2,3 并将其组合到单个表中的开销的情况下在 SQL 中实现相同的目标?
If I understand correctly, you want to do three aggregations in one.如果我理解正确,您希望将三个聚合合二为一。 One method is to use
cross join
to bring in the information to distinguish each aggregation:一种方法是使用
cross join
引入信息来区分每个聚合:
select col2, col3, field_name,
(case when field_name = 'col3' then col3
when field_name = 'col4' then col4
when field_name = 'col5' then col5
end) as field_value,
count(*) as cnt
from t cross join
(select 'col3' as field_name union all
select 'col4' as field_name union all
select 'col5' as field_name
) f
group by col2, col3, field_name, field_value
order by field_name, col2 desc, col3;
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