Oracle SQL Query按不同表中的列值排序

Question

I'm rather new to sql and am struggling with a statement. For simplicity, let's say I have two tables - Table - JourneyOrder, and Table - ItemsToBuy.

JourneyOrder has list of cities, index of a particular city in a journey and who is taking the journey. So:

City   Index Name
London 1     John
Sydney 2     John
Paris  3     John
Berlin 1     Jack
Paris  2     Jack

The other table has a list of items to buy, containing location (as in City), who needs to buy an item, and different characteristics of an item.

Item   Location   Weight   Price   Responsible
Pencil London     1        2       John
Glue   London     2        5       John
Car    Paris      1000     12000   John
Wallet Paris      3        20      Jack

I want to select all items a particular person needs to buy and order them by location. So if John's first route is London, I want items you can buy in London displayed first.

At the moment, I can use the following:

SELECT itb.item, itb.location, itb.price
FROM ItemsToBuy itb,
WHERE itb.responsible = 'John'
ORDER BY CASE
WHEN itb.location = 'London' THEN '1' 
WHEN itb.location = 'Sydney' THEN '2' 
WHEN itb.location = 'Paris'  THEN '3' 

Now this is obviously terrible, as I need to 'hardcode' the order by part according to the journey each responsible is taking, how can I make it so it matches location of items table to city from journey table and uses the index from the journey table when these match.

Answer 1

I think you just want a join :

SELECT itb.item, itb.location, itb.price
FROM ItemsToBuy itb JOIN
     JourneyOrder jo
     ON itb.name = jo.name AND itb.location = jo.city
WHERE itb.responsible = 'John'
ORDER BY jo.index;