Question

我正在使用sqlite3，并试图获取不同组的中位数。我目前正在使用以下查询

with data as (
select
t1.Name,
t1.Direction,
t1.Time a,
t2.Time b
from
cart t1 join cart t2 on t1.Time < t2.Time and t1.Name = t2.Name and t1.Direction = t2.Direction)
select Name, Direction, (a+b)/2.0 val from data order by Name, Direction, val

输出以下内容：

"Name"  "Direction" "val"
"asdf"  "w"         "1.5"
"asdf"  "w"         "2.0"
"asdf"  "w"         "2.5"
"asdf"  "z"         "3.5"
"asdf"  "z"         "4.0"
"asdf"  "z"         "4.5"
"fdas"  "w"         "7.5"
"fdas"  "w"         "8.0"
"fdas"  "w"         "8.5"
"fdas"  "z"         "5.5"
"fdas"  "z"         "6.0"
"fdas"  "z"         "6.5"

从这一点出发，我想找到所有唯一的“名称/方向”对的中值。

预期结果：

Name Direction Val
asdf w         2.0
asdf z         4.0
fdas w         8.0
fdas z         6.0

或者如果更容易使用，还可以使用以下输出将“名称”和“方向”合并为一个唯一的ID

Name   Val
asdfw  2.0
asdfz  4.0
fdasw  8.0
fdasz  6.0

原始表格数据如下：

"Name"  "Direction" "Time"
"fdas"  "w" "8"
"fdas"  "w" "9"
"fdas"  "w" "7"
"fdas"  "z" "7"
"fdas"  "z" "6"
"fdas"  "z" "5"
"asdf"  "z" "5"
"asdf"  "z" "4"
"asdf"  "z" "3"
"asdf"  "w" "3"
"asdf"  "w" "2"
"asdf"  "w" "1"

更新

通过以下查询，我已经更加接近了。剩下的唯一问题是找到所需的偏移量查询。目前，我已经使用以下offset 3对其进行了硬编码，但是需要获取中心行。我已经尝试过(select idx from calcs where data2.Name = calcs.Name and data2.Direction = calcs.Direction)，但是随后出现此错误no such table: calcs: with data2。

with data2 as (
with data as (
select
t1.Name,
t1.Direction,
t1.Time a,
t2.Time b
from
cart t1 join cart t2 on t1.Time < t2.Time and t1.Name = t2.Name and t1.Direction = t2.Direction)
select Name, Direction, (a+b)/2.0 c from data order by Name, Direction, c
) select
    Name,
    Direction,
    (select c from
        (select c from data2 where data2.Name = calcs.Name and data2.Direction = calcs.Direction
            order by c
            limit 1
            offset 2 ) subset
    order by subset.c) tt
from
(select Name, Direction, round(COUNT(*)/2.0) idx from data2 group by Name, Direction) calcs

Answer 1

使用另一个子查询

with data as (
select
t1.Name,
t1.Direction,
t1.Time a,
t2.Time b
from
cart t1 join cart t2 
on t1.Time < t2.Time and t1.Name = t2.Name 
and t1.Direction = t2.Direction
),
data2 as 
  (
 select Name, Direction, 
 (a+b)/2.0 as val 
 from data 
 order by Name, Direction, val
  ) select Name,Direction,avg(val) as mdval from data2 group by 
  Name,Direction

或者仅在第二个查询中使用聚合

with data as (
select
t1.Name,
t1.Direction,
t1.Time a,
t2.Time b
from
cart t1 join cart t2 on t1.Time < t2.Time and t1.Name = t2.Name and t1.Direction = t2.Direction
)
select Name, Direction, avg((a+b)/2.0) as val
from data group by Name, Direction
order by Name, Direction, val

SQLite3中位数与2列偏移量子查询分组

更新

1 个答案: