I'm working on a small project involving oracle database,
and I have the following tables:
CUSTOMER ( Cid, CName, City, Discount )
PRODUCT ( Pid, PName, City, Quantity, Price )
ORDERS ( OrderNo, Month, Cid, Aid, Pid, OrderedQuantity, Cost )
How can retrieve the names of all customers who ordered all the products?
For example if customer x ordered product1, product2 and product3 (which are all the products the company offers) he will be selected. And if customer y only ordered product 1 and 2 but not 3 he will not be selected.
How can I achieve this?
You want "relational division".
select *
from customer c
where not exists( -- There are no product
select 'x'
from product p
where not exists( -- the customer did not buy
select 'x'
from orders o
where o.cid = c.cid
and o.pid = p.id));
or
select c.cid
,c.name
from customer c
join orders o using(cid)
group
by c.id
,c.name
having count(distinct o.pid) = (select count(*) from product);
Here is a great article by Joe Celko that shows several ways of implementing relational division (and variations): Divided We Stand: The SQL of Relational Division
You can use group by and use a having clause to demand that the customer has ordered all products there are:
select c.CName
from Customers c
join Orders o
on o.Cid = c.Cid
group by
c.Cid
, c.CName
having count(distinct o.Pid) = (select count(*) from products)
IMHO more readable than the "relational divison" approach, but less efficient.
Related
I have the following tables
Customer (CID, name, address)
Orders (CID, BID, onDate, quantity)
Device (DID, title, IMEI, price, MID)
Manufacturer (MID, name, address)
What SQL statement would allow me to retrieve the ID's and names of all
the customers who have spent atleast X amount (lets say 350 for example)
on devices made my the manufacturer "Sony". The list should include the total amount of money spent by each customer on those devices.
I assume that the table Orders contains a column DID (BID is a typo, right?) that relates it to the table device.
Join the tables, group by customer to aggregate and set the condition in the HAVING clause:
select c.CID, c.name,
sum(o.quantity * d.price) total_amount
from customer c
inner join orders o on o.CID = c.CID
inner join device d on d.DID = o.DID
inner join manufacturer m on m.MID = d.MID
where m.name = 'Sony'
group by c.CID, c.name
having sum(o.quantity * d.price) >= 350
Below is a SQL script to see how many customers purchased both products, as well as how many customers purchased either of the two products.
I would like to be able to return a result set with one column for the first product, one column for the second, one column for Count with Both, and one column for Count with Either.
Instead it returns a column for each of the counts and a single NULL column for the ProductID.
SELECT
COUNT(DISTINCT b.CustomerID) AS "Count with Both",
COUNT(DISTINCT c.CustomerID) AS "Count with Either",
b.ProductID
FROM
LocationCode z
LEFT JOIN
(SELECT DISTINCT ProductID, CustomerID
FROM LocationCode a
WHERE a.ProductID IN ('MP040') AND a.ProductID IN ('OG010')) b ON z.CustomerID = b.CustomerID
LEFT JOIN
(SELECT DISTINCT ProductID, CustomerID
FROM LocationCode b
WHERE b.ProductID IN ('MP040', 'OG010')) c ON z.CustomerID = c.CustomerID
GROUP BY
b.ProductID
If I understand correctly, you can use a self-join and aggregation. The following does what you want for all pairs of products:
with cp as (
select customerid, productid,
count(*) over (partition by customerid) as num_customers
from locationcode
group by customerid, productid
)
select cp1.productid, cp2.productid, cp1.cnt as cnt1, cp2.cnt as cnt2,
count(*) as both
from cp cp1 join
cp cp2
on cp1.customerid = cp2.customerid and
cp1.productid < cp2.productid
group by cp1.productid, cp2.productid, cp1.cnt, cp2.cnt ;
You can of course add where filters if you only want results for certain products.
Write a query that determines the customer that has spent the most on music for each country. Write a query that returns the country along with the top customer and how much they spent. For countries where the top amount spent is shared, provide all customers who spent this amount.
You should only need to use the Customer and Invoice tables.
i want to select the customer with the maximum money spent for each country and there is two customers have the same money spent and the same country so when using group by country i got only 1 customer what should i do ?
select c.CustomerId,c.FirstName,c.LastName, c.Country , max(c.Invoices) as TotalSpent
from
(select * , sum(i.Total) as 'Invoices'
from Customer d
join Invoice i on i.CustomerId = d.CustomerId
group by i.CustomerId
) c
group by c.Country
the table i got is the same expected table except 1 customer
Consider joining unit level with two aggregate queries: 1) first to calculate total amount by CustomerId and Country and 2) second to calculate max total amount by Country.
Below assumes your database supports Common Table Expression (CTE) using the WITH clause (nearly supported by all major commercial or open-source RDBMS's). CTE here avoids the need to repeat sum_agg as a subquery.
with sum_agg AS (
select i.CustomerId, sub_c.Country, sum(i.Total) as Sum_Amount
from Customer sub_c
join Invoice i on i.CustomerId = sub_c.CustomerId
group by i.CustomerId, sub_c.Country
)
select c.CustomerId, c.FirstName, c.LastName, c.Country, max_agg.Max_Sum
from Customer c
join sum_agg
on c.CustomerId = sum_agg.Customer_Id and c.Country = sum_agg.Country
join
(select Country, max(Sum_Amount) as Max_Sum
from sum_agg
group by Country
) max_agg
on max_agg.Country = sum_agg.Country and max_agg.Max_Sum = sum_agg.Sum_Amount
Your inner query is almost correct. It should be
select d.*, sum(i.Total) as Invoices
from Customer d
join Invoice i on i.CustomerId = d.CustomerId
group by d.CustomerId
It is allowed to use d.* here, as we can assume d.CustomerId to be the table's primary key, so all columns in the table are functionally dependent on it. If we grouped by d.country instead for instance, that would not be the case and d.* would be forbidden in the select clause (as well as d.firstname etc.). We can only select columns we grouped by (directly or indirectly) and aggregates such as MIN, MAX, SUM etc.
This query gives you the totals per customer along with the customers' countries.
But then you are taking this result and group by country. If you do this, you can only access country and its aggregates. Selecting c.CustomerId for instance is invalid, as there is no the customer ID per country. If your DBMS allows this, it it flawed in this regard and you get a kind of random result.
If your DBMS features window functions, you can get the maximum amounts per country on-the-fly:
select customerid, firstname, lastname, country, invoices
from
(
select
c.*,
sum(i.total) as invoices,
max(sum(i.total)) over (partition by c.country) as max_sum
from customer c
join invoice i on i.customerid = c.customerid
group by c.customerid
) per_customer
where invoices = max_sum
order by country, customerid;
Otherwise you'd have to use your inner query twice, once to get the country totals, once to get the customers matching these totals:
select
c.customerid, c.firstname, c.lastname, c.country,
sum(i.total) as invoices
from customer c
join invoice i on i.customerid = c.customerid
group by c.customerid
having (c.country, invoices) in
(
select country, max(invoices)
from
(
select
--c.customerid, <- optional, it may make this query more readable
c.country,
sum(i.total) as invoices
from customer c
join invoice i on i.customerid = c.customerid
group by c.customerid
) per_customer
);
I'm having trouble creating a query with a sub query to find the one customer in my DB who has made the most purchases. I need to list his/her full name, product name, price and quantity. Here is what I have so far
select first_name ||' '|| last_name "FullName", pt.name p.price, sum(ps.quantity)
from customers c
join purchases ps on c.customer_id = ps.customer_id
join products p on p.product_id = ps.product_id
join product_types pt on p.product_type_id = pt.product_type_id;
I need to use these three tables
Customers Table
Customer_ID
First_Name
Last_Name
DOB
Phone
Purchases Table
Product_ID
Customer_ID
Quantity
Products Table
Product_ID
Product_Type_ID
Name
Description
Price
Product Types Table
Product_Type_ID
Name
I am confused as where I should place the sub query (in the select row, from, having or where clause), if the arithmetic function should be placed in the select outer query or sub query. I know there are Nested subqueries, Correlated subqueries, Multiple-column subqueries, Multiple-row subqueries, Single-row subqueries. By the way, I am trying to do this in Oracle.
Here is an image with my result, except I removed sum from quantity column. Also, updated link.
(http://i1294.photobucket.com/albums/b618/uRsh3RRaYm0nD/Capture100_zps1f951b07.jpg)
I'm sorry, I forgot to include a fourth table, as you can see there are two name columns, in products table and product type table. The difference is that in products table "Name" is the specific name of the product, as shown in my link. The product type "Name" column is the more general name of the product, such as books, dvds, cds, etc. I need to include the product type "Name column in my query not product's name column. Therefore, the end result should look something like this
FullName ProductTypeName Price Quantity
John Brown Book Sumof4books 4
John Brown DVD Sumof2DVDs 2
John Brown Magazine Sumof1Mag 1
Here's one way to do it. It uses an analytic function to order customers by the total quantity of purchases: row_number() over (order by sum(quantity) desc). If there's more than one person with the same quantity, this will pick out only one.
It then takes this customer id and joins the rest of the tables in the obvious way to get the break down by product type.
Select
c.FullName,
pt.name,
Sum(p.price * ps.quantity) price,
sum(ps.quantity) quantity
From (
Select
c.Customer_ID,
c.first_name ||' '|| c.last_name FullName,
row_number() over (order by Sum(Quantity) desc) r
From
Purchases ps
Inner Join
Customers c
On ps.Customer_ID = c.Customer_ID
Group By
c.Customer_ID,
c.first_name ||' '|| c.last_name
) c
Inner Join
Purchases ps
On c.Customer_ID = ps.Customer_ID
Inner Join
Products p
On ps.Product_ID = p.Product_ID
Inner Join
Product_Types pt
On p.Product_Type_ID = pt.Product_Type_ID
Where
c.r = 1
Group By
c.FullName,
pt.name
Example Fiddle
For the second problem (show the customer who has the highest quantity for each product type, together with what they've spent on that product type)
Select
c.FullName,
c.name,
c.price,
c.quantity
From (
Select
c.first_name ||' '|| c.last_name FullName,
pt.name,
sum(p.price * ps.quantity) price,
sum(ps.quantity) quantity,
row_number() over (partition by pt.name order by Sum(Quantity) desc) r
From
Purchases ps
Inner Join
Customers c
On ps.Customer_ID = c.Customer_ID
Inner Join
Products p
On ps.Product_ID = p.Product_ID
Inner Join
Product_Types pt
On p.Product_Type_ID = pt.Product_Type_ID
Group By
c.first_name ||' '|| c.last_name,
pt.name
) c
Where
c.r = 1
Example Fiddle
Here is the general idea. You can adapt it for your database tables.
select fred, barney, maxwilma
from bedrock join
(select max(wilma) maxwilma
from bedrock
group by fred ) flinstone on wilma = maxwilma
SELECT CLIENT.CLIENTNO, CLIENT.CNAME, SUM(PURCHASE.AMOUNT) AS AMOUNT
FROM CLIENT
INNER JOIN PURCHASE
ON CLIENT.CLIENTNO = PURCHASE.CLIENTNO
WHERE CLIENT.CLIENTNO IN (
SELECT CLIENTNO
FROM (
SELECT PURCHASE.CLIENTNO, SUM(PURCHASE.AMOUNT) AS AMOUNT
FROM PURCHASE
GROUP BY PURCHASE.CLIENTNO
ORDER BY AMOUNT DESC
)
WHERE ROWNUM = 1)
GROUP BY CLIENT.CLIENTNO, CLIENT.CNAME;
select first_name ||' '|| last_name "FullName",name,quantity from customers,purchases,products where products.product_id = purchases.product_id and purchases.customer_id = customers.customer_id order by quantity;
This is the query you want
I am using three tables in a PostgreSql database as:
Customer(Id, Name, City),
Product(Id, Name, Price),
Orders(Customer_Id, Product_Id, Date)
and I want to execute a query to get from them "the customers that have have ordered at least two different products alnong with the products". The query I write is:
select c.*, p.*
from customer c
join orders o on o.customer_id = c.id
join product p on p.id = o.product_id
group by (c.id)
having count(distinct o.product_id)>=2
It throws the error:
"column "p.id" must appear in the GROUP BY clause or be used in an aggregate function
LINE 1: select c.*, p.*".
However if I remove the the p.* from select statement (assuming that I one does not want the products, only the customers), it runs fine. How can I get the products as well?
Update: Having ordered two or more products, a customer must appear on the output as many times as its product he has ordered. I want as output a table with 5 columns:
Cust ID | Cust Name | Cust City | Prod ID | Prod Name | Prod Price
Is it possible in SQL given that group by should be used? Shoul it be used on more than one columns on different tables?
Try this out :
SELECT distinct c.* ,p.*
FROM Customer c
JOIN
(SELECT o.customer_id cid
FROM Product P
JOIN Orders o
ON p.id= o.product_id
GROUP BY o.customer_id
HAVING COUNT(distinct o.product_id)>=2) cp
ON c.id =cp.cid
JOIN Orders o
on c.id=o.customer_id
JOIN Product p
ON o.product_id =p.id
I hope it solves your problem.
I think you can use following query for this question -
SELECT C1.*, p1.*
FROM Customer C1
JOIN Orders O1 ON O1.Customer_Id = C1.Id
JOIN Product P1 ON P1.Id = O1.Product_Id
WHERE C1.Id IN (SELECT c.Id
FROM Customer c
JOIN Orders o ON o.Customer_Id = c.Id
GROUP BY (c.Id)
HAVING COUNT(DISTINCT o.Product_Id) >= 2)