MS SQL Merge two queries to get One Result - sql

Question

I am implementing a vehicle management system. I have two different queries, one for fetching all vehicles of an agency and one for fetching drivers. Every vehicle is has a driver assigned to it at a time.
Now I want to merge these two queries to returns vehicles details along with details of the driver assigned to the vehicle.
1st query to get drivers and their names:
SELECT UserInfo.Name
FROM DriverInfo INNER JOIN UserInfo ON DriverInfo.Email = UserInfo.Email
INNER JOIN Agency ON UserInfo.AgencyID = Agency.AgencyID
WHERE (UserInfo.AgencyID = 1)
ORDER BY DriverInfo.DriverId DESC
2nd query to get vehicles details:
SELECT Vehicle.VehicleRegNum AS [Registration Number],
Vehicle.EngineNum AS [Engine Number],
Vehicle.FileRef AS [File Refrence],
Type.Name AS Type,
Make.Name AS Make ,
Vehicle.DriverID AS DriverID
FROM Vehicle INNER JOIN Type ON Vehicle.Type = Type.TypeId
INNER JOIN Make ON Vehicle.Make = Make.MakeId
WHERE (Vehicle.Approve = 1)
AND (Vehicle.AgencyId = 1)
AND (Vehicle.Maintained = 1)
ORDER BY Vehicle.VId DESC
In this query, I am getting the DriverID
and in the DriverInfo:
DriverId, LicenseType, AppointmentDate, LicenseExpiryDate, ContractExpiryDate, Email

Answer 1

Just add on the additional tables in your join.
SELECT Vehicle.VehicleRegNum AS [Registration Number],
Vehicle.EngineNum AS [Engine Number],
Vehicle.FileRef AS [File Refrence],
Type.Name AS Type,
Make.Name AS Make,
DriverInfo.DriverId,
DriverInfo.LicenseType,
DriverInfo.AppointmentDate,
DriverInfo.LicenseExpiryDate,
DriverInfo.ContractExpiryDate,
DriverInfo.Email
FROM Vehicle
INNER JOIN Type
ON Vehicle.Type = Type.TypeId
INNER JOIN Make
ON Vehicle.Make = Make.MakeId
INNER JOIN DriverInfo
ON Vehicle.DriverID = DriverInfo.DriverId
INNER JOIN UserInfo
ON DriverInfo.Email = UserInfo.Email
INNER JOIN Agency
ON UserInfo.AgencyID = Agency.AgencyID
AND Vehicle.AgencyID = Agency.AgencyID
WHERE (Vehicle.Approve = 1)
AND (Vehicle.AgencyId = 1)
AND (Vehicle.Maintained = 1)
ORDER BY Vehicle.VId DESC

Answer 2

I believe the following will work, depending on your requirements you might wanna change the JOIN type of DriverInfo:
SELECT Vehicle.VehicleRegNum AS [Registration Number]
,Vehicle.EngineNum AS [Engine Number]
,Vehicle.FileRef AS [File Refrence]
,Type.NAME AS Type
,Make.NAME AS Make
,UserInfo.NAME AS Driver
FROM Vehicle
INNER JOIN Type ON Vehicle.Type = Type.TypeId
INNER JOIN Make ON Vehicle.Make = Make.MakeId
LEFT JOIN DriverInfo ON DriverInfo.DriverID = Vehicle.DriverID
LEFT JOIN UserInfo ON DriverInfo.Email = UserInfo.Email
AND (UserInfo.AgencyID = 1)
--Agency is never used, so don't join?
--LEFT JOIN Agency ON UserInfo.AgencyID = Agency.AgencyID
WHERE (Vehicle.Approve = 1)
AND (Vehicle.AgencyId = 1)
AND (Vehicle.Maintained = 1)
ORDER BY Vehicle.VId DESC