以平均每小时转置 SQLite 行和列
我在 SQLite 中有一个名为 param_vals_breaches 的表，如下所示:
I have a table in SQLite called param_vals_breaches that looks like the following:
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，它会显示一个特定队列(例如a")，平均 param_val 和 breach_count每个参数按小时计算.因此，转置数据以获得如下所示的内容:
I want to write a query that will show me a particular queue (e.g. "a") with the average param_val and breach_count for each param on an hour by hour basis. So transposing the data to get something that looks like this:
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?我不知道该怎么做.谢谢！
is this possible? I'm not sure how to go about it. Thanks!
推荐答案
SQLite 没有 PIVOT 函数，但您可以使用带有 CASE 表达式的聚合函数将行转换为列:
SQLite does not have a PIVOT function but you can use an aggregate function with a CASE expression to turn the rows into columns:
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 SQL Fiddle with Demo
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