Sorting based on multiple conditions - sql

Question

I am doing a exercise
I'll fire a query on the DB and get some 500 results. Now i want to sort this list based on some conditions and present the sorted list in client side.
I am using Java/Java EE and MySQL server 5.5
Conditions are like this,
Example: Consider a table having listed with cars
So, i ll fire a query on the table and it will list some 500 cars. now i want to sort this list based on user criteria.
conditions are age of car, colour of car and facilities of cars. List should be sorted like this
First appears the list of cars which satisfies all three conditions ie., same age as mentioned by end user, same colour and with all facilities user selected.
Second appears any 2 conditions satisfying cars list and one condition not satifying.
Third appears any one condition satisfying cars list and not the other two.
And finally appears the list of cars of which no conditions are satisfied.
How can i achieve this. I have searched in google, asked in irc channels regarding this. Couldn't get any help.
I have tried using RANK function by defining the CASES and finally order by RANK. It works for me while the conditions fields (columns) are of same table. In my case the fields are from a parent table as well as its child tables which has many to one relationship with its parent. Like in this example, age and color of the cars are stored in parent table and facilities that cars has are stored in another table. I tried doing the same using inner join, but no luck.
I tried something like this:
Query:
select distinct t0.id,t0.name,t0.price,
CASE
WHEN
t1.age='2' AND t1.colour='Red' AND t2.facilities_id=9 THEN 1
WHEN
t1.age='2' AND t1.colour='Red' AND t2.facilities_id!=9 THEN 2
WHEN
t1.age='2' AND t1.colour!='Red' AND t2.facilities_id=9 THEN 3
WHEN
t1.age!='2' AND t1.colour='Red' AND t2.facilities_id=9 THEN 4
WHEN
t1.age!='2' AND t1.colour='Red' AND t2.facilities_id!=9 THEN 5
WHEN
t1.age='2' AND t1.colour!='Red' AND t2.facilities_id!=9 THEN 6
WHEN *
t1.age!='2' AND t1.colour!='Red' AND t2.facilities_id=9 THEN 7
ELSE 8
END as pre_status
from cars_listing t0
inner join
cars_listing_details t1
on t0.id=t1.mg_listing_id
inner join
cars_facilities_listing t2
on t1.cars_listing_id=t2.listing_id
where t0.type='new_cars'
order by pre_status
Thanks in advance for helping.

Answer 1

try ordering by something like...
order by
case when first_condition then 1 else 0 end
+ case when second_condition then 1 else 0 end
+ case when third_condition then 1 else 0 end DESC
select distinct
t0.id,
t0.name,
t0.price,
case when t1.age = '2' then 1 else 0 end as MatchedAge,
case when t1.colour='Red' then 1 else 0 end as MatchedColor,
case when t2.facilities_id = 9 THEN 1 else 0 end as MatchedFacility
from
cars_listing t0
inner join cars_listing_details t1
on t0.id = t1.mg_listing_id
inner join cars_facilities_listing t2
on t1.cars_listing_id = t2.listing_id
where
t0.type = 'new_cars'
order by
case when t1.age = '2' then 1 else 0 end
+ case when t1.colour='Red' then 1 else 0 end
+ case when t2.facilities_id = 9 THEN 1 else 0 end DESC
If one field is a higher priority -- such as a red car, you could even give that more weight than the other in the order by... So a Red car at Facility 5 would show before a Blue car at facility 9 just by changing the order by to something like
order by
case when t1.age = '2' then 1 else 0 end
+ case when t1.colour='Red' then 5 else 0 end <-- applyi higher Wgt to color match vs other criteria
+ case when t2.facilities_id = 9 THEN 1 else 0 end DESC

Answer 2

Well, I have done Dynamic sql where condition in my project. It might help you. I have created a stored procedure for SELECT query. (I have done it in SQL Server 2008 R2). Tell me if you need more help.
USE [DATABASE_NAME]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE PROCEDURE [dbo].[PROCEDURE_NAME]
#Id int = NULL,
#Requester varchar(20) = NULL,
#Suggester varchar(20) = NULL
AS
BEGIN
DECLARE #sql nvarchar(4000)
SELECT #sql='SELECT Id, Suggester, Requester from DATABASE_NAME.dbo.TABLE_NAME WHERE 1=1 '
If (#Id) IS NOT NULL
SELECT #sql=#sql + ' AND Id=(#Id) '
If (#Suggester) IS NOT NULL
SELECT #sql=#sql + ' AND Suggester like (#Suggester) '
If (#Requester) IS NOT NULL
SELECT #sql=#sql + ' AND Requester like (#Requester) '
EXEC sp_executesql #sql, N'#id int, #Requester varchar(20), #Suggester varchar(20)',
#Id, #Requester, #Suggester
END
GO
Here in this SP; Id,Requester,Suggester are field names.