Question

简化我的数据库样本是一个表格，如

        CN REG#         CAPACITY
---------- ---------- ----------
         0 LUCY02          43000
         6 QRT834           5550
         3 SYF777           3333
        12 PKR768           1234
         5 SST005          12000
         6 KKK007          10000
         3 PKR008          22000

这是通过连接两个表创建的。这是连接声明：

select count(tp.reg#) as cn,t.reg#,  CAPACITY
from truck t
join trip tp 
on  t.reg# = tp.reg#
group by tp.reg#,  CAPACITY, t.reg#

现在，我如何编写一个语句来仅打印具有最小出现次数和非零次数的行。在我们的例子中它是3。

预期输出

     3 SYF777           3333
     3 PKR008          22000

到目前为止，我所做的却不起作用：

select count(tp.reg#) as cn,t.reg#,  CAPACITY
from truck t
left join trip tp 
on  t.reg# = tp.reg#
left join
(                       
    select dd, min(d) as ds
    from(
        select count(*)as d, ti.CAPACITY, ti.reg# as dd
        from truck ti, trip tp 
        where tp.reg# = ti.reg#
        group by ti.reg#, ti.CAPACITY
    )
    group by dd
)
on t.reg# = dd
group by tp.reg#,  CAPACITY, t.reg#

Answer 1

如果您想根据＆＃34; count＆＃34;这样的聚合函数过滤您的查询，只需在＆＃34;中添加＆＃34;语句：

select count(tp.reg#) as cn,t.reg#,  CAPACITY
from truck t
join trip tp 
on  t.reg# = tp.reg#
group by tp.reg#,  CAPACITY, t.reg#
having count(tp.reg#) >= 3

如果您想要动态最小的查询记录，可以使用以下代码：

select count(tp.reg#) as cn,t.reg#,  CAPACITY
from truck t
join trip tp 
on  t.reg# = tp.reg#
group by tp.reg#,  CAPACITY, t.reg#
having count(tp.reg#) = (select distinct top 1 count(tp.reg#) cn
                         from truck t
                         join trip tp 
                         on  t.reg# = tp.reg#
                         group by tp.reg#,  CAPACITY, t.reg#
                         having count(tp.reg#) >0
                         order by cn)

Answer 2

嗨，你可以试试这个，

 select * from 
       (select count(tp.reg#) as cn,t.reg#,  CAPACITY
       from truck t
       join trip tp 
       on  t.reg# = tp.reg#
       group by tp.reg#,  CAPACITY, t.reg#)
  where cn = (select min(cn) from (select count(tp.reg#) as cn,t.reg#,  CAPACITY
                                      from truck t
                                      join trip tp 
                                      on  t.reg# = tp.reg#
                                      where cn > 0
                                      group by tp.reg#,  CAPACITY, t.reg#))

我希望对你有用... 感谢

Answer 3

您只需要对动态视图进行几次转换，并在中途添加过滤：

    select min(y.cn) , y.REG#, y.CAPACITY
from 
(
    select x.CN, x.REG#, x.CAPACITY 
    FROM 
    (
        select count(tp.reg#) as cn,t.reg#,  CAPACITY
        from truck t
        join trip tp 
        on  t.reg# = tp.reg#
        group by tp.reg#,  CAPACITY, t.reg#
    ) X
    WHERE x.cn != 0
) y
group by y.REG#, y.CAPACITY

如何只选择表中出现次数最少的记录？

3 个答案: