SQL Nested Query based on value of Dependent Column - sql

Question

In the below table structure, TB_Vehicles is the Master table and TB_Cars, TB_Bikes, TB_Cars are Satellite tables which hold more info about respective vehicles.
**TB_Scooters**
V_NAME V_ID V_YEAR V_TYPE V_MILEAGE
Activa 10 2003 Scooter 45
Access 20 2004 Scooter 50
**TB_Bikes**
V_NAME V_ID V_YEAR V_TYPE V_ENGINE
Karizma 30 2001 Bike 180
Pulsar 40 2008 Bike 150
**TB_Cars**
V_NAME V_ID V_YEAR V_TYPE V_CAR_TYPE
Linea 50 2011 Car Sedan
i20 60 2012 Car Sedan
**TB_Vehicles**
V_NAME V_ID V_YEAR V_TYPE V_COLOR V_AVAILABLE
Activa 10 2003 Scooter Black Yes
Access 20 2004 Scooter Black No
Karizma 30 2001 Bike Red Yes
Pulsar 40 2008 Bike Black Yes
Linea 50 2011 Car White No
i20 60 2012 Car Red Yes
I want users to search using the Name. So, when users enter Name as 'Access', my query should give all information about that vehicle, including that from Satellite Tables (using both TB_Vehicles and TB_Scooters).
SELECT * FROM TB_Vehicles
WHERE V_NAME = 'Access';
Similarly, if user enters 'Linea', it should give info from TB_Vehicles and TB_Cars tables.
So, with V_NAME as input, I'll find V_TYPE from TB_Vehicles table, and using that, I need to identify which satellite table, I need to join to retrieve more info.
How do I do this? Can you please help me with the query? Do I need to use CASE or DECODE to achieve this?
EDIT:
The requirement here is to display only those columns which are applicable for that particular vehicle type. So, when user gives 'Access' as input, it should display all columns from TB_Vehicles table, and V_MILEAGE from TB_Scooters table.
I was thinking whether this can be done using CASE or DECODE, where I first identify the type (V_TYPE) of the vehicle from TB_Vehicles table using the input name (V_NAME), and then based on this V_TYPE, I'll search the relevant table and display only relevant columns.
When Input Name is 'Access', then result should be:
V_NAME V_ID V_YEAR V_TYPE V_COLOR V_AVAILABLE V_MILEAGE
Access 20 2004 Scooter Black No 50
When Input Name is 'i20', then result should be:
V_NAME V_ID V_YEAR V_TYPE V_COLOR V_AVAILABLE V_CAR_TYPE
i20 60 2012 Car Red Yes Sedan

Answer 1

You shouldn't be storing the name in both the vehicles tables and the subtables. If this is common information, then just store it in the vehicles table. This is true of all the common columns.
Next, when you access data, do it by bringing together all the tables:
select v.*,
s.v_mileage, b.v_engine, c.v_car_type
from TB_vehicles v left join
TB_Scooters s
on s.v_id = v.v_id and v.type = 'scooter' left join
TB_Bikes b
on b.v_id = v.v_id and v.type = 'bike' left join
TB_Cars c
on c.v_id = v.vid and v.type = 'car';
From this query, you can then choose the row and the fields that you want.
However, you need to work on normalizing your data structure so fields like v_year are only in one table.

Answer 2

Thanks Gordon! Appreciate your help over this...
For others with similar query, please look into the above response from Gordon as well as the below link:
http://www.orafaq.com/forum/t/189451/180198/