仅在满足特定条件时如何选择记录

Question

表A包含客户名称，服务日期和诊断。

如果要换油，我想选择客户，服务日期和该天的所有诊断。如果不进行换油，我什么都不想要。

我尝试过

select customer, servicedate, diagnosis
from A
where customer in (select customer from A where diagnosis = 'oilchange')
    and servicedate in (select servicedate from A where diagnosis = 'oilchange')

预期产量

Answer 1

尝试类似

SELECT all.customer, all.servicedate, all.diagnosis
FROM A all INNER JOIN A oilchange 
ON all.customer=oilchange.customer AND oilchange.diagnosis='oilchange'

Answer 2

首先获取diagnosis = 'oil change'所在的日期和客户，然后加入表格：

select A.customer, A.servicedate, A.diagnosis
from A inner join (
  select customer, servicedate
  from A
  where diagnosis = 'oil change' 
) B on B.customer = A.customer and B.servicedate = A.servicedate

或使用EXISTS：

select t.customer, t.servicedate, t.diagnosis
from A t
where exists (
  select 1 from A
  where customer = t.customer and servicedate = t.servicedate and diagnosis = 'oil change'
)

请参见demo。
结果：

> customer | servicedate         | diagnosis  
> :------- | :------------------ | :----------
> Smith    | 01/01/2019 00:00:00 | Spark plugs
> Smith    | 01/01/2019 00:00:00 | ValveCG    
> Smith    | 01/01/2019 00:00:00 | oil change 
> Smith    | 01/01/2019 00:00:00 | alignment  
> John     | 06/01/2019 00:00:00 | puncture   
> John     | 06/01/2019 00:00:00 | oil change 
> John     | 06/01/2019 00:00:00 | Wipers     
> John     | 06/01/2019 00:00:00 | engine    

Answer 3

尝试一下：

select customer, servicedate, diagnosis
from A as a1, A as a2
where a1.customer = a2.customer and a1.servicedate = a2.servicedate and a2.diagnosis = 'oilchange'

Answer 4

如果我理解正确的话

首先确定换油的客户

;with OilChange
AS(
    select customer, servicedate
    from A
    where diagnosis = 'oilchange' 
)
--then get the rest of the data
select tbl.customer, tbl.servicedate, tbl.diagnosis
from A tbl
INNER JOIN OilChange OC on OC.Customer = tbl.Customer and OC.Servicedate = tbl.ServiceDate