仅在满足特定条件时如何选择记录

Question

Table A has customer names, service dates, and diagnosis.

I want to select the customer, the date of service and all diagnosis for that particular day if an oil change was done. If an oil change was not done, I don't want anything at all.

I have tried

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')

Expected Output

Answer 1

Try something like

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

First get the dates and customers where there is diagnosis = 'oil change' and join to the table:

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

Or with 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'
)

See the demo .
Results:

> 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

Try this:

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

if I understand this correctly

First identify the customers who had an oil change

;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