Troubles with nested queries...

Question

I have this query which works perfectly:

SELECT *
FROM Customer
WHERE SacCode IN
(
    SELECT SacCode
    FROM SacCode
    WHERE ResellerCorporateID = 392
    ORDER BY SacCode
)
AND CustomerID IN
(
    SELECT CxID
    FROM CustAppointments
    WHERE AppRoomID IN
    (
     SELECT AppRoomID
     FROM ClinicRooms
     WHERE ClinID IN
     (
      SELECT ClinID
      FROM AppClinics
      WHERE ClinDate >='20090101'
      AND ClinDate <='20091119'
     )
    )
)

However, I need to see the value of ClinDate (inside the last nested query)...

How do I do it?

Thanks.

Answer 1

Think I'd use derived table in the FROM statement rather than 3 deep nested query, will allow you to access values and will look a LOT better.

Answer 2

You'll need to copy the subselects to the FROM clause or rewrite the query using JOINs.

Answer 3

it should look something like this:

SELECT c.*, a.ClinDate

FROM Customer c

inner join CustAppointments ca
inner join ClinicRooms cr
inner join AppClinics a

where c.SacCode IN
(
    SELECT SacCode
    FROM SacCode
    WHERE ResellerCorporateID = 392
    ORDER BY SacCode
)

and c.CustomerID = ca.CxID
and ca.AppRoomID = cr.AppRoomID
and cr.ClinID = a.ClinID

and a.ClinDate >='20090101' 
and a.ClinDate <='20091119'

Answer 4

I'd rewrite the query using joins. Then, you can access any data from any of the joined tables.

For example, you could rewrite your query like this:

SELECT c.*, ac.ClinDate
FROM Customer c
  JOIN SacCode sc ON sc.SacCode = c.SacCode
  JOIN CustAppointments ca ON ca.CustomerID = c.CustomerID
  JOIN ClinicRooms cr ON cr.AppRoomID = ca.AppRoomID
  JOIN AppClinic ac ON ac.ClinID = cr.ClinID
WHERE ac.ClinDate >='20090101'
  AND ac.ClinDate <='20091119'
  AND sc.ResellerCorporateID = 392