This is a query on the Sakila sample database. I'm not sure why COUNT is returning '1' for every row - I want it to count the number of customers in that country/city/postal_code combination.
SELECT country.country_id, country.country, city.city_id, city.city, address.postal_code, COUNT(*) AS 'Customer Count'
FROM address
INNER JOIN city ON city.city_id = address.city_id
INNER JOIN country ON country.country_id = city.country_id
INNER JOIN customer ON customer.address_id = address.address_id
GROUP BY country.country, city.city, address.postal_code
Any ideas on what I'm doing wrong?
Here is some of the output:
Because you are not getting multiple records per GROUP.
The COUNT() function returns the number of records that match the same GROUP BY.
Also this query doesn't seem to work since you're selecting ID's but not grouping on them.
Related
I tried to write a query, but unfortunately I didn't succeed.
I want to know how many packages delivered over a given period by a person.
So I want to know how many packages were delivered by John (user_id = 1) between 01-02-18 and 28-02-18. John drives another car (another plate_id) every day.
(orders_drivers.user_id, plates.plate_name, orders.delivery_date, orders.package_amount)
I have 3 table:
orders with plate_id delivery_date package_amount
plates with plate_id plate_name
orders_drivers with plate_id plate_date user_id
I tried some solutions but didn't get the expected result. Thanks!
Try using JOINS as shown below:
SELECT SUM(o.package_amount)
FROM orders o INNER JOIN orders_drivers od
ON o.plate_id=od.plate_id
WHERE od.user_id=<the_user_id>;
See MySQL Join Made Easy for insight.
You can also use a subquery:
SELECT SUM(o.package_amount)
FROM orders o
WHERE EXISTS (SELECT 1
FROM orders_drivers od
WHERE user_id=<user_id> AND o.plate_id=od.plate_id);
SELECT sum(orders.package_amount) AS amount
FROM orders
LEFT JOIN plates ON orders.plate_id = orders_drivers.plate_id
LEFT JOIN orders_driver ON orders.plate_id = orders_drivers.plate_id
WHERE orders.delivery_date > date1 AND orders.delivery_date < date2 AND orders_driver.user_id = userid
GROUP BY orders_drivers.user_id
But seriously, you need to ask questions that makes more sense.
sum is a function to add all values that has been grouped by GROUP BY.
LEFT JOIN connects all tables by id = id. Any other join can do this in this case, as all ids are unique (at least I hope).
WHERE, where you give the dates and user.
And GROUP BY userid, so if there are more records of the same id, they are returned as one (and summed by their pack amount.)
With the AS, your result is returned under the name 'amount',
If you want the total of packageamount by user in a period, you can use this query:
UPDATE: add a where clause on user_id, to retrieve John related data
SELECT od.user_id
, p.plate_name
, SUM(o.package_amount) AS TotalPackageAmount
FROM orders_drivers od
JOIN plates p
ON o.plate_id = od.plate_id
JOIN orders o
ON o.plate_id = od.plate_id
WHERE o.delivery_date BETWEEN convert(datetime,01/02/2018,103) AND convert(datetime,28/02/2018,103)
AND od.user_id = 1
GROUP BY od.user_id
, p.plate_name
It groups rows on user_id and plate_name, filter a period of delivery_date(s) and then calculate the sum of packageamount for the group
in this cust_id is a foreign key and ords returns the number of orders for every customers
SELECT cust_name, (
SELECT COUNT(*)
FROM Orders
WHERE Orders.cust_id = Customers.cust_id
) AS ords
FROM Customers
The output is correct but i want to filter it to retrieve only the customers with less than a given amount of orders, i don't know how to filter the subquery ords, i tried WHERE ords < 2 at the end of the code but it doesn't work and i've tried adding AND COUNT(*)<2 after the cust_id comparison but it doesn't work. I am using MySQL
Use the HAVING clause (and use a join instead of a subquery).....
SELECT Customers.cust_id, Customers.cust_name, COUNT(*) ords
FROM Orders, Customers
WHERE Orders.cust_id = Customers.cust_id
GROUP BY 1,2
HAVING COUNT(*)<2
If you want to include people with zero orders you change the join to an outer join.
There is no need for a correlated subquery here, because it calculates the value for each row which doesn't give a "good" performance. A better approach would be to use a regular query with joins, group by and having clause to apply your condition to groups.
Since your condition is to return only customers that have less than 2 orders, left join instead of inner join would be appropriate. It would return customers that have no orders as well (with 0 count).
select
cust_name, count(*)
from
customers c
left join orders o on c.cust_id = o.cust_id
group by cust_name
having count(*) < 2
working with mySql I would like to list all purchases that customers made on a specific cathegory of products.
So, I had 3 tables: customers (idCustomer, Name) , cathegories (idCategory, CategoryName) and orders (idOrder, idCustomer, idCathegory, Qty, Price)
But I want a listing with ALL of the customers.
Not only the one who bought that specific idCategory
I thought something like:
select sum(Orders.Qty), Customers.Name
from Orders
right join Customers on Orders.idCustomer = Customer.idCustomer
where Orders.idCategory = 'Notebooks'
group by Orders.idCategory
but this statement only lists the records for customers who exists in Orders table.
And I want all of them ( the one who didnt buy, with qty =0 )
thanks in advance
Most people find left join easier to follow than right join. The logic for left join is to keep all rows in the first table, plus additional information from the remaining tables. So, if you want all customers, then that should be the first table.
You will then have a condition on the second table. Conditions on all but the first table should be in the on clause rather than a where. The reason is simple: when there is no match, then the value will be NULL and the where condition will fail.
So, try something like this:
select sum(o.Qty) as sumqty, c.Name
from Customers c left join
Orders o
on o.idCustomer = c.idCustomer and
o.idCategory = 'Notebooks'
group by c.Name;
Finally, the group by should have a relationship to the select clause.
Try this query
select sum(Orders.Qty), Customers.Name
from Customers
right join Orders on Customer.idCustomer = Orders.idCustomer and Orders.idCategory = 'Notebooks'
group by Customers.Name
I have searched high and low and can't seem to get a way to do what I want. I have a table with some customers, some products and their relationships.
I want to count the amount of returned rows from this part of the query
SELECT id
FROM customer
WHERE customer.name = 'SMITH'
OR customer.name = 'JONES'
I also want to return the ids that match SMITH and JONES (or other customer names chosen). I want to use the count of the returned rows as a variable (denoted as #var). I only want to return the products, id, and count that match my variable.
My questions are:
Is there a way that this can be done in a single SQL query?
Is there a way to return the count as well as the values?
I don't want to have to throw this into a PHP script or the like.
SELECT x.pId, p.productdesc, count(x.dId) as count
FROM
(
SELECT DISTINCT cId, pId
FROM Client
WHERE cId IN
(
SELECT id
FROM customer
WHERE customer.name = 'SMITH'
OR customer.name = 'JONES'
)
)x
JOIN Products p ON x.pId = p.id
GROUP BY x.pId
HAVING count = #var
Thanks,
M
This is sort of a 'literal' answer to what your asked, as you can use subqueries in the having clause. However, with more information (sample data and expected result) there may be a better way of doing what you want.
select x.pid, p.productdesc, count(x.pid) as count
from (select distinct cl.cid, cl.pid
from client cl
join customer cu
on cl.cid = cu.id
where cu.name in ('SMITH', 'JONES')) x
join products p
on x.pid = p.id
group by x.pid, p.productdesc
having count(x.pid) = (select count(*)
from customer
where name in ('SMITH', 'JONES'))
The following sql call works fine, returns the correct total retail for customers:
SELECT customer.id,
customer.first_name,
customer.last_name,
SUM(sales_line_item_detail.retail) AS total_retail
FROM sales_line_item_detail
INNER JOIN sales_header
ON sales_header.id = sales_line_item_detail.sales_header_id
INNER JOIN customer
ON customer.id = sales_header.customer_id
GROUP BY sales_header.customer_Id
ORDER BY total_Retail DESC
LIMIT 10
However, i need it to return the customers telephone and email addresses as well.. please keep in mind that not all customers have an email address and telephone number. whenever i left join the email and numbers tables, it throws the total_retail amount off by thousands and I am not sure why.
The following query gives completely wrong results for the total_retail field:
SELECT customer.id,
customer.first_name,
customer.last_name,
IF(
ISNULL( gemstore.customer_phone_numbers.Number),
'No Number..',
gemstore.customer_phone_numbers.Number
) AS Number,
IF(
ISNULL(gemstore.customer_emails.Email),
'No Email...',
gemstore.customer_emails.Email
) AS Email,
SUM(sales_line_item_detail.retail) AS total_retail,
FROM sales_line_item_detail
INNER JOIN sales_header
ON sales_header.id = sales_line_item_detail.sales_header_id
INNER JOIN customer
ON customer.id = sales_header.customer_id
LEFT JOIN gemstore.customer_emails
ON gemstore.customer_emails.Customer_ID = gemstore.customer.ID
LEFT JOIN gemstore.customer_phone_numbers
ON gemstore.customer_phone_numbers.Customer_ID = gemstore.customer.ID
GROUP BY sales_header.customer_Id
ORDER BY total_Retail DESC
LIMIT 10
Any help figuring out why it is throwing off my results is greatly appreciated.
Thanks!
Is it possible that there are multiple records for a Customer_ID in either the customer_emails or customer_phone_numbers tables?
You'll be matching too many records. Try the query without the group by clause and you'll see which ones and how. Most likely the left join's will duplicate order rows on every customer email/phone match.
I am not totally sure, as i can't test this, but the following might be happening.
If there are more than one email or phone number per customer the final result might get multiplied, because of the new joins.
Imagine the query without the group_by and join to sales:
CustomerId Email phoneNumber
1 test#gmx.com 0122233
1 mail#yahoo.com 0122233
The user in this example has 2 mailadresses.
If you would now add the join to sales and the group by, you would have doubled total_retail.
If this should be the case, replacing the LEFT JOIN with an LEFT OUTER JOIN should do the trick. In that case you will however only see the first email/phonenumer of the customer.