平均每小时平均转置SQLite行和列

Question

我在SQLite中有一个名为param_vals_breaches的表，如下所示：

id    param       queue       date_time              param_val    breach_count
1     c           a           2013-01-01 00:00:00    188          7
2     c           b           2013-01-01 00:00:00    156          8
3     c           c           2013-01-01 00:00:00    100          2
4     d           a           2013-01-01 00:00:00    657          0
5     d           b           2013-01-01 00:00:00    23           6
6     d           c           2013-01-01 00:00:00    230          12
7     c           a           2013-01-01 01:00:00    100          0
8     c           b           2013-01-01 01:00:00    143          9
9     c           c           2013-01-01 01:00:00    12           2
10    d           a           2013-01-01 01:00:00    0            1
11    d           b           2013-01-01 01:00:00    29           5
12    d           c           2013-01-01 01:00:00    22           14
13    c           a           2013-01-01 02:00:00    188          7
14    c           b           2013-01-01 02:00:00    156          8
15    c           c           2013-01-01 02:00:00    100          2
16    d           a           2013-01-01 02:00:00    657          0
17    d           b           2013-01-01 02:00:00    23           6
18    d           c           2013-01-01 02:00:00    230          12

我想编写一个查询，以小时为基础，向我显示一个特定的队列（例如“ a ”），每个队列的平均 参数 为 param_val 和
违规 数。因此，转置数据以获得如下所示的内容：

Results for Queue A

         Hour 0         Hour 0              Hour 1         Hour 1              Hour 2         Hour 2
param    avg_param_val  avg_breach_count    avg_param_val  avg_breach_count    avg_param_val  avg_breach_count
c        xxx            xxx                 xxx            xxx                 xxx            xxx
d        xxx            xxx                 xxx            xxx                 xxx            xxx

这可能吗？我不确定该怎么做。谢谢！

Answer 1

SQLite没有PIVOT函数，但是您可以将聚合函数与CASE表达式结合使用，以将行变成列：

select param,
  avg(case when time = '00' then param_val end) AvgHour0Val,
  avg(case when time = '00' then breach_count end) AvgHour0Count,
  avg(case when time = '01' then param_val end) AvgHour1Val,
  avg(case when time = '01' then breach_count end) AvgHour1Count,
  avg(case when time = '02' then param_val end) AvgHour2Val,
  avg(case when time = '02' then breach_count end) AvgHour2Count
from
(
  select param,
    strftime('%H', date_time) time,
    param_val,
    breach_count
  from param_vals_breaches
  where queue = 'a'
) src
group by param;

参见带有演示的SQL Fiddle