如何獲取數據庫表中的前x％值

Question

如何獲取數據庫表中前x％的值。

例如，我有一個日誌文件，我加載到數據庫表中。我想拋出最長的1％的請求，因爲他們歪曲數據。

任何簡單的方法來做到這一點？

順便說一句我正在使用德比數據庫。

謝謝

Answer 1

您是否需要累計或個人百分比？我不知道使用Derby計算累計總數的方法，但我知道H2數據庫/ MySQL的一種方法。因此，只有我的示例的第一部分適用於德比。對於MySQL，您需要用CAST（...作爲整數）替換CAST（... AS INTEGER）：

drop table test; 
create table test(data int); 
create index idx_test_data on test(data desc); 
insert into test values(1), (1), (1), (2); 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test select data from test; 
insert into test values(100), (200), (800); 
select sum(data), count(*) from test; 

select data, (data * 100./(select sum(data) from test)) percent 
from test where data * 100./(select sum(data) from test) < 1 order by data desc; 

select @acc := 0, @total := sum(data) from test; 
create table pa as select data, cast(@acc := @acc + (data * 100./@total) as integer) percent_acc 
from test order by data desc; 
select * from pa where percent_acc > 2 limit 10; 
drop table pa;