如何在r中使用sql将两个或多个表连接成一个表

我已经编写了以下代码，我想把这些表合并成一个大表；那么，如何使用SQL在R中实现这一点呢

user_lessthan10per  <- sqldf("select count(uid) as count_of_students
                       from adopted_user_point
                        where points_scored between 0 and (1469*0.1)")

---

user\u lessthan10per您可以使用条件聚合。这将返回一行三列：

select sum(case when points_scored between 0 and (1469*0.1) then 1 else 0
           end) as cnt1,
       sum(case when points_scored >(1469*0.1) and points_scored <= (1469*0.2) then 1 else 0 
           end) as cnt2,
       sum(case when points_scored >(1469*0.2) and points_scored <= (1469*0.3) then 1 else 0
           end) as cnt3
from adopted_user_point;

我会用不同的名称来命名最初的选择，二者分别命名为“u_0_10”、“u_10_20”、“u_20_30”，以明确“用户少于30%”实际上是“用户btwn20_30”，但现在它们在全球环境中是R数据帧，您真的不需要
sdldf
将它们放在一起：

user_under30per <- rbind(user_lessthan10per.
                        user_lessthan20per,
                        user_lessthan30per)

user\u低于30%
select sum(case when points_scored between 0 and (1469*0.1) then 1 else 0
           end) as cnt1,
       sum(case when points_scored >(1469*0.1) and points_scored <= (1469*0.2) then 1 else 0 
           end) as cnt2,
       sum(case when points_scored >(1469*0.2) and points_scored <= (1469*0.3) then 1 else 0
           end) as cnt3
from adopted_user_point;

select (case when points_scored between 0 and (1469*0.1) then 'Group1'
             when points_scored >(1469*0.1) and points_scored <= (1469*0.2) then 'Group2'
             when points_scored >(1469*0.2) and points_scored <= (1469*0.3) then 'Group3'
             else 'Other'
        end) as cnt3, count(*) as count_of_students
from adopted_user_point
group by (case when points_scored between 0 and (1469*0.1) then 'Group1'
               when points_scored >(1469*0.1) and points_scored <= (1469*0.2) then 'Group2'
               when points_scored >(1469*0.2) and points_scored <= (1469*0.3) then 'Group3'
               else 'Other'
          end);

user_under30per <- rbind(user_lessthan10per.
                        user_lessthan20per,
                        user_lessthan30per)

 one_and_two <- sqldf("select * from lessthan10per union all 
                                       select * from lessthan20per")
 all_three <- sqldf("select * from one_and_two union all 
                                       select * from lessthan30per")