postgresql 視窗函式排序例項

經常遇到一種應用場景，將部分行的內容進行彙總、比較、排序。

比如資料表名稱test.test2

select num,province from test.test2

得到結果：

1828;"

黑龍江"
137;"
黑龍江"
184;"
黑龍江"
183;"福建"
125;"福建"
143;"福建"
119;"海南"
109;"海南"
132;"
海南"

那麼我希望將內容按照省份來排序，那麼需要：

select

province, 
num,
sum(num) over (partition by province order
by num desc rows between unbounded preceding and
current row) as
all_num
from test.test2

得到結果：

"海南";132;132

"海南";
119;251
"海南";
109;360
"福建";
183;183
"福建";
143;326
"福建";
125;451
"黑龍江";
1828;1828
"黑龍江";
184;2012
"黑龍江";
137;2149

如果還要看每行佔整個省份的百分比，那麼需要

with tmp as

(select
province, 
num,
sum(num) over (partition by province order
by num desc rows between unbounded preceding and
current row) as
curr_num,
sum(num) over (partition by province rows between unbounded preceding and unbounded following) as
all_num
from
test.test2
)select
province, 
num,
all_num,
curr_num
/all_num
from tmp

結果如下

"海南";132;360;0.36666666666666666667

"海南";
119;360;0.69722222222222222222
"海南";
109;360;1.00000000000000000000
"福建";
183;451;0.40576496674057649667
"福建";
143;451;0.72283813747228381375
"福建";
125;451;1.00000000000000000000
"黑龍江";
1828;2149;0.85062819916240111680
"黑龍江";
184;2149;0.93624941833410888785
"黑龍江";
137;2149;1.00000000000000000000

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