我如何从其他表中获得具有“相同”名称的所有值的客户

Question

I have problem. I have tables:

Customer(cid,etc..),
Motorbike(mid, name, etc..) 

and table

Rent(rid,cid, mid, check_in, check_out, etc..).

Name of motorbike includes brand (like Yamaha XT660 R, Yamaha R6, Honda CBF125R, etc.)

My task is to find customers who rented all Yamaha or Suzuki motorbikes. My query: select c.name, m.name, count(c.name) from motorbike m, rent r, customer c where c.cid = r.cid AND r.mid = m.mid and (m.name like 'Yamaha%' or m.name like 'Suzuki%') group by c.ime

Answer 1

This sounds like you should be able to solve it with a straightforward JOIN query:

SELECT
    r.rid, m.name, c.*
FROM
    Rent r
    JOIN Motorbike m
        ON r.mid = m.mid
    JOIN Costumer c
        ON r.cid = c.cid
WHERE
    m.name LIKE 'Yamaha%'
    OR m.name LIKE 'Honda%'
ORDER BY
    m.name, r.check_in

The above will select the rental ID, bike name and full customer information for each rental for all Yamaha / Honda bikes.

If you want to get a "unique" list of customers that rented said bikes, but not the full rental history, you can leverage GROUP BY :

SELECT
    c.cid, m.name, COUNT(*) AS num_rentals
FROM
    Rent r
    JOIN Motorbike m
        ON r.mid = m.mid
    JOIN Costumer c
        ON r.cid = c.cid
WHERE
    m.name LIKE 'Yamaha%'
    OR m.name LIKE 'Honda%'
GROUP BY
    c.cid

Answer 2

Try this:

SELECT C.*,m.mid,m.name as BikeName,R.check_out,R.check_in
FROM Costumer C JOIN
     Rent R ON R.cid=C.cid JOIN
     Motorbike M ON R.bid=M.mid
WHERE m.name LIKE 'Yamaha%'
   OR m.name LIKE 'Honda%'

Answer 3

You can get customers who rented at least on e Yamaha and at least on Suzuki by using group by :

select c.*
from Rent r join
     Motorbike m
     on r.mid = m.mid join
     Customer c
     on r.cid = c.cid
group by c.id
having sum(m.name LIKE 'Yamaha%') > 0 and
       sum(m.name LIKE 'Honda%') > 0;

Each condition in the having clause counts the number of motorcycles of a given type. You want at least one of each.