Question -
Display customer Id, name, and total number of orders, for orders handled by salesman Marshall, but only if customer name begins on General or ends on Electric. Exclude customers who placed a single order, but include customers without orders as well. Sort the result based on the total number of orders descending and then by name ascending.
Do not use LIKE operator and do not join 3 tables.
Questions output
Current Query
SELECT c.customer_id,
c.name,
Count(o.order_id) "# of Orders"
FROM customers c
left join orders o
ON c.customer_id = o.customer_id
WHERE Substr(c.name, 1, 7) = 'General'
OR Substr(c.name, -8) = 'Electric'
AND o.order_id IN (SELECT o.order_id
FROM orders o,
order_items oi
WHERE o.order_id = oi.order_id
AND o.salesman_id = (SELECT employee_id
FROM employees
WHERE
last_name = 'Marshall')
GROUP BY o.order_id
HAVING Count(customer_id) > 1)
GROUP BY c.customer_id,
c.name;
Database -
Not sure what I am doing wrong here.
That's a really contrived assignment... Here is one option:
select c.customer_id, c.customer_name, count(o.orderid) cnt
from customers c
left join orders o
on o.customer_id = c.customer_id
and (select last_name from employee e where e.employee_id = o.salesman_id) = 'Marshall'
where substr(c.name, 1, 7) = 'General' or substr(c.name, -8) = 'Electric'
group by c.customer_id, c.customer_name
having count(o.orderid) <> 1
The base idea is a left join. The where clause filters on the customer name - without like: you had that already.
To filter on the salesman name without an additional join, we use a correlated subquery in the on clause of the left join. There is no need to bring order_items, nor to select again from orders here.
Finally, the filtering on the order counts goes to the having clause.
Related
I have two tables, customers and orders, and I want to get the number of orders made by each customer.
I tried
SELECT orders.order_id, customers.customer_id,
FROM customers
INNER JOIN orders ON orders.customer_id = customers.customer_id
but I can't count number of orders
You are describing aggregation:
SELECT c.customer_id, count(*) no_orders
FROM customers c
INNER JOIN orders o ON o.customer_id = c.customer_id
GROUP BY c.customer_id
If you also want customers that have no order, use a LEFT JOIN instead, or a correlated subquery:
SELECT
c.customer_id,
(SELECT COUNT(*) FROM orders o WHERE o.customer_id = c.customer_id) no_orders
FROM customers c
Need help with a query to returns each individuals most recent order, date of the order, number of products in the order and the total amount. I am kind of stuck trying to get the number of products and total.
Here are the table diagrams
Not sure if I should be using multiple joins or subqueries:
SELECT FirstName, LastName, MAX(O.OrderDate), O.OrderDate
FROM Customer C
INNER JOIN Order O ON C.CustomerID = O.CustomerID
It is always good practice to start from assumed dim tables such as product.This Query should help. It is better to aggregate quantity and amount to get results at aggregate level
SELECT FirstName
,LastName
,max(o.orderdate) Orderdate
,Sum(Quantity) Quantity
,Sum(TotalAmount) TotalAmount
FROM Product p
INNER JOIN Orderitem oi
ON Oi.product_id = p.id
INNER JOIN
ORDER o
ON o.id = oi.order_id
INNER JOIN Customer c
ON c.id = o.Customer_id
GROUP BY FirstName
,LastName
not sure if you want aggregations but here you go:
SELECT customer.firstname, customer.lastname, COUNT(DISTINCT orderitem.productid), [order].totalamount
FROM [order] LEFT JOIN customer ON [order].customerid=customer.id LEFT JOIN orderitem ON order.id=orderitem.orderid
WHERE [order].date=MAX([order].date)
GROUP BY customer.firstname,customer.lastname, [order].totalamount
Still don't know why you are applying a where clause for the last order, it's up to you to keep or not the where condtion.
I was going through an example of LEFT JOIN on w3schools.com.
http://www.w3schools.com/sql/sql_join_left.asp
SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders
ON Customers.CustomerID=Orders.CustomerID
ORDER BY Customers.CustomerName;
The above query will return me all customers with No Orders as NULL Order ID+ All customers having Orders with their Order Ids
How should I modify this query so that it returns All Customers with No Orders + All Customers having Orders with Order date as '1996-09-18'
Thanks in advance.
If you want customers with no orders and those with a specific order date, then you want a WHERE clause:
SELECT c.CustomerName, o.OrderID
FROM Customers c LEFT JOIN
Orders o
ON c.CustomerID = o.CustomerID
WHERE (o.CustomerID is NULL) OR (o.OrderDate = DATE '1996-09-18)
ORDER BY c.CustomerName;
If you wanted all customers with their order on that date (if they have one), then you would move the condition to the ON clause:
SELECT c.CustomerName, o.OrderID
FROM Customers c LEFT JOIN
Orders o
ON c.CustomerID = o.CustomerID AND o.OrderDate = DATE '1996-09-18
ORDER BY c.CustomerName;
Note the difference: the first filters the customers. The second only affects what order gets shown (and NULL will often be shown).
I am counting how many times a company has ordered. Then I am only showing if a company has ordered less than 5 times. I am then checking it against the table with all company names to see what company has not ordered, which would not show up on the order table, then add their name on the displayed list.
What I have tried:
Select Orders.CustomerID, Count(Orders.CustomerID) AS OrderCount
From Orders Left Join Customers
On Orders.CustomerID = Customers.CustomerID
Group By Orders.CustomerID
Having Count(Orders.CustomerID) <5
This is totally wrong:
Select CustomerID
From Customers
Where EXISTS
(Select CustomerID, Count(CustomerID) AS 'OrderCount'
From Orders
Group BY CustomerID
Having Count(Orders.CustomerID) < 5)
I need to somehow compare the list of names before I ask it to see which ones have ordered less than 5 times.
Thanks
If you want to use LEFT JOIN, interchange the table names since you want to show values from Customers, otherwise use RIGHT JOIN instead.
SELECT Customers.CustomerID,
COUNT(Orders.CustomerID) AS OrderCount
FROM Customers
LEFT JOIN Orders
ON Orders.CustomerID = Customers.CustomerID
GROUP BY Customers.CustomerID
HAVING COUNT(Orders.CustomerID) < 5
using EXISTS()
SELECT CustomerID
FROM Customers c
WHERE EXISTS
(
SELECT 1
FROM Orders o
WHERE o.CustomerID = c.CustomerID
GROUP BY CustomerID
HAVING COUNT(CustomerID) < 5
)
Try this:
SELECT C.CustomerID, C.CustomerName, COUNT(O.CustomerID) AS OrderCount
FROM Customers C
LEFT JOIN Orders O ON O.CustomerID = C.CustomerID
GROUP BY C.CustomerID
HAVING OrderCount < 5
ORDER BY OrderCount, C.CustomerName
I just took a final exam and one of the questions asked me to double join three tables, and report the max sale payout for each salesperson.
The tables have the following variables:
Salesperson(id, name)
Order(orderid, order_date, Cust_id, Saleperson_id, amount)
Customer(id, name)
After joining:
select salesperson.Name, Orders.Number, customer.Name, Orders.Amount
from Orders
join salesperson
on orders.Salesperson_id = salesperson.ID
join Customer
on customer.ID = orders.cust_id
What the instructed wanted was for me to find each salesperson's maximum sell (as found by order.amount). He also wanted the salesperson (salesperson.name), the order number of the max sale (orders.number), the customer the sale was with (customer.name), and the max sale amount. What is the most efficient way to do this problem? I have tried to use "group by salesperson.name", but I cannot because the orders.number and customer.name are never held in the aggregation.
I finished the problem this way
select
salesperson.name as Sales_Person,
orders.number as Order_Number,
customer.Name as Customer_Name,
orders.Amount as Sale_Amount
from salesperson
left join Orders
on salesperson.ID = orders.Salesperson_id
left join Customer
on orders.cust_id = customer.ID
where orders.Amount in (select max(orders.Amount)
from salesperson
join Orders
on salesperson.ID = orders.Salesperson_id
join Customer
on orders.cust_id = customer.ID
group by salesperson.name)
I know this is a bad way to do it. For instance, what if two different salesperson's max sale was equivalent? Max and min are not like count and sum because it is picking out one line from a aggregation, but the rules still apply. Also, you might notices that there is no real unique identifier in the joined table other than order.number which is not useful. Therefore, I would have to use some composite of salesperson.name and order.number.
Also, what do I do if I have to pick the top three sales for each salesperson? Should such an output be totally different code-wise than what would be required from just the first sale?
I keep bumping me head against this problem, and I would love to have a more professional approach to this problem.
SELECT
M.max_amount,
S.Name,
O.Number,
C.Name
FROM orders O
JOIN salesperson S
ON S.Salesperson_id = O.Salesperson_id
JOIN customer C
ON C.Customer_id = O.Customer_id
JOIN (
SELECT Salesperson_id, MAX(amount) max_amount
FROM Order
GROUP BY Salesperson_id
) M
ON M.Salesperson_id = O.Salesperson_id AND M.max_amount = O.amount
For the top 3:
SELECT
M.Amount,
S.Name,
O.Number,
C.Name
FROM orders O
JOIN salesperson S
ON S.Salesperson_id = O.Salesperson_id
JOIN customer C
ON C.Customer_id = O.Customer_id
CROSS APPLY (
SELECT TOP 3 Amount
FROM Order
WHERE Salesperson_id = O.Salesperson_id
ORDER BY Amount DESC
) M