I have a schema with customers, orders and order dates.
A customer can have orders in multiple dates. I need a calculated member to bring the first order date and the second order date with other associated metrics.
I was able to get the first order date and associated data using min(order date) as a first order but having issues querying for the second order date. Any suggestion would help! Thanks
my query
---I have all the information in one table so my query looks like
Select customerid, order id, min(orderdate) as firstorderdate,...
From customer Where first ordedate between 01/01/2015’ and GETDATE()
(since I only want those customers who made their first purchase this year)
Query their second purchase
Select customerid, orderid, orderdate from ( select customerid,
orderid, orderdate, rwo_number() over (partition by customerid,
orderid order by orderdate) rn from customer
Where rn<=2
Without seeing your current query, it's difficult to understand. I assume your current query is like this:
select c.customerid, o.orderid, min(od.orderdate)
from customers c
join orders o on c.customerid = o.customerid
join orderdates od on o.orderid = od.orderid
group by c.customerid, o.orderid
Another way of doing the same query is to use row_number. Doing it this way, you're not restricted to just the first in the group:
select customerid, orderid, orderdate
from (
select c.customerid, o.orderid, od.orderdate,
row_number() over (partition by c.customerid, o.orderid
order by od.orderdate) rn
from customers c
join orders o on c.customerid = o.customerid
join orderdates od on o.orderid = od.orderid
) t
where rn <= 2
Related
Im currently working with the northwind database and want to see the companies with more orders place in 1997. Im being ask to use windows function so i wrote this
select c.customerid,
c.companyname,
rank() over (order by count(orderid) desc )
from customers c
inner join orders o on c.customerid = o.customerid
where date_part('year',orderdate) = 1997;
However this code ask me to use GROUP BY with c.customerid. And i simply don't understand why. Supposedly this code will give me all the customers id and names and after that the window function kicks in giving them a rank base on the amount of orders. So why group them?
Here:
rank() over (order by count(orderid) desc )
You have an aggregate function in the over() clause of the window function (count(orderid)), so you do need a group by clause. Your idea is to put in the same group all orders of the same customer:
select c.customerid,
c.companyname,
rank() over (order by count(*) desc) as rn
from customers c
inner join orders o on c.customerid = o.customerid
where o.orderdate = date '1997-01-01' and o.orderdate < '1998-01-01'
group by c.customerid;
Notes:
Filtering on literal dates is much more efficient than applying a date function on the date column
count(orderid) is equivalent to count(*) in the context of this query
Postgres understands functionnaly-dependent column: assuming that customerid is the primary key of customer, it is sufficient to put just that column in the group by clause
It is a good practice to give aliases to expressions in the select clause
Another good practice is to prefix all columns with the (alias of) table they belong to
You would use it correctly in an aggregation query. That would be:
select c.customerid, c.companyname, count(*) as num_orders,
rank() over (order by count(*) desc) as ranking
from customers c inner join
orders o
on c.customerid = o.customerid
where date_part('year',orderdate) = 1997
group by c.customerid, c.companyname;
This counts the number of orders per customer in 1997. It then ranks the customers based on the number of orders.
I would advise you to use:
where orderdate >= '1997-01-01' and
orderdate < '1998-01-01'
For the filtering by year. This allows Postgres to use an index if one is available.
First of all: I've found some possible answers to my problem in the previously asked questions, but I've encountered problems with getting them to work properly. I know the question was already asked, but the answers always were working code with little to no explaination on the method used.
So: I've got to find out when a customer reached the VIP status, which is when value of his orders exceeds 50 000. I've got 2 tables: one with orderid, customerid and orderdate, and second with orderid, quantity and unitprice.
The result of the query I'm writing should be 3 colums wide, one with the customerid, one with true/false named "is VIP?", and the third is the date of getting the VIP status(which is the date of order that summed with the previous ones gave a result of over 50 000)-the last one should be blank if the customer didn't reach the VIP status
select o.customerid, sum(od.quantity*od.unitprice),
case
when sum(od.quantity*od.unitprice)>50000 then 'VIP'
else 'Normal'
end as 'if vip'
from
orders o join [Order Details] od on od.orderid=o.orderid
group by o.customerid
That is as far as I got with the code, it returns the status of the customer and now I need to get the date when that happend.
.
You can easily calculate a running total using a window functions:
select o.customerid,
o.orderdate,
sum(od.quantity*od.unitprice) over (partition by o.customerid order by orderdate) as running_sum,
from orders o
join Order_Details od on od.orderid = o.orderid
order by customer_id, orderdate;
Now you need to find a way to detect the first row, where the running total exceeds the threshold:
The following query starts numbering the rows in a descending manner once the threshold is reached. Which in turn means the row with then number 1 is the first one to cross the threshold:
with totals as (
select o.customerid,
o.orderdate,
sum(od.quantity*od.unitprice) over (partition by o.customerid order by orderdate) as running_sum,
case
when
sum(od.quantity*od.unitprice) over (partition by o.customerid order by orderdate) > 50000 then row_number() over (partition by o.customerid order by orderdate desc)
else 0
end as rn
from orders o
join Order_Details od on od.orderid = o.orderid
)
select *
from totals
where rn = 1
order by customerid;
SQLFiddle example: http://sqlfiddle.com/#!6/a7f18/3
You get the cumulative sum using an Analytic Function, SUM OVER. And then add an aggregate to find the minimum date:
with cte as
( select o.customerid,
o.orderdate,
case when sum(od.quantity*od.unitprice) -- running total
over (partition by o.customerid
order by orderdate
rows unbounded preceding) > 50000
then 'Y'
else 'N'
end as VIP
from orders o
join Order_Details od on od.orderid = o.orderid
)
select customerid,
MAX(VIP) AS "isVIP?", -- either 'N' or 'Y'
MIN(CASE WHEN VIP = 'Y' THEN orderdate END) AS VIP_date -- only when VIP status reached
from cte
group by customerid
order by customers;
See fiddle
Not going to complicate the answer with logic to show 'vip' and 'vip date'. This will give you a running total for each customer order.
select o.orderid, o.customerid, o.orderdate, sum(od.quantity*od.unitprice) 'Total', (
select sum(od.quantity * od.unitprice) total
from orders o2
join [Order Details] od2 on od2.orderid=o2.orderid
where o2.orderID <= o.orderID
and o2.customerid = o.customerid) 'RunningTotal'
from orders o
join [Order Details] od
on od.orderid=o.orderid
group by o.orderid, o.customerid, o.orderdate
order by o.customerid
To answer your question on how to approach, you could consider going for an SQL trigger which runs on each update to the tables involved and sets the status when the threshold is hit.This would set the date as and when the event happens.
Another approach would be to use a stored procedure wherein you can use a loop top iterate over the records and arrive at the date.
The choice can be made based on the volume of the data, with the former bring suitable for extremely large amounts of data.
I am pretty new to using MS SQL 2012 and I am trying to create a query that will:
Report the order id, the order date and the employee id that processed the order
report the maximum shipping cost among the orders processed by the same employee prior to that order
This is the code that I've come up with, but it returns the freight of the particular order date. Whereas I am trying to get the maximum freight from all the orders before the particular order.
select o.employeeid, o.orderid, o.orderdate, t2.maxfreight
from orders o
inner join
(
select employeeid, orderdate, max(freight) as maxfreight
from orders
group by EmployeeID, OrderDate
) t2
on o.EmployeeID = t2.EmployeeID
inner join
(
select employeeid, max(orderdate) as mostRecentOrderDate
from Orders
group by EmployeeID
) t3
on t2.EmployeeID = t3.EmployeeID
where o.freight = t2.maxfreight and t2.orderdate < t3.mostRecentOrderDate
Step one is to read the order:
select o.employeeid, o.orderid, o.orderdate
from orders o
where o.orderid = #ParticularOrder;
That gives you everything you need to go out and get the previous orders from the same employee and join each one to the row you get from above.
select o.employeeid, o.orderid, o.orderdate, o2.freight
from orders o
join orders o2
on o2.employeeid = o.employeeid
and o2.orderdate < o.orderdate
where o.orderid = #ParticularOrder;
Now you have a whole bunch of rows with the first three values the same and the fourth is the freight cost of each previous order. So just group by the first three fields and select the maximum of the previous orders.
select o.employeeid, o.orderid, o.orderdate, max( o2.freight ) as maxfreight
from orders o
join orders o2
on o2.employeeid = o.employeeid
and o2.orderdate < o.orderdate
where o.orderid = #ParticularOrder
group by o.employeeid, o.orderid, o.orderdate;
Done. Build your query in stages and many times it will turn out to be much simpler than you at first thought.
It is unclear why you are using t3. From the question it doesn't sound like the employee's most recent order date is relevant at all, unless I am misunderstanding (which is absolutely possible).
I believe the issue lies in t2. You are grouping by orderdate, which will return the max freight for that date and employeeid, as you describe. You need to calculate a maximum total from all orders that occurred before the date that the order occurred on, for that employee, for every row you are returning.
It probably makes more sense to use a subquery for this.
SELECT o.employeeid, o.orderid, o.orderdate, m.maxfreight
FROM
orders o LEFT OUTER JOIN
(SELECT max(freight) as maxfreight
FROM orders AS f
WHERE f.orderdate <= o.orderdate AND f.employeeid = o.employeeid
) AS m
Hoping this is syntactically correct as I'm not in front of SSMS right now. I also included a left outer join as your previous query with an inner join would have excluded any rows where an employee had no previous orders (i.e. first order ever).
You can do what you want with a correlated subquery or apply. Here is one way:
select o.employeeid, o.orderid, o.orderdate, t2.maxfreight
from orders o outer apply
(select max(freight) as maxfreight
from orders o2
where o2.employeeid = o.employeid and
o2.orderdate < o.orderdate
) t2;
In SQL Server 2012+, you can also do this with a cumulative maximum:
select o.employeeid, o.orderid, o.orderdate,
max(freight) over (partition by employeeid
order by o.orderdate rows between unbounded preceding and 1 preceding
) as maxfreight
from orders o;
I am a beginner with SQL and I cannot seem to come up with a correct query for this question:
Use a correlated subquery to return one row per customer, representing the customer’s oldest order (the one with the earliest date). Each row should include these three columns: EmailAddress, OrderID, and OrderDate.
I started by joining orders and customers table. EmailAddress is the only column needed from customers table.
SELECT EmailAddress, OrderDate, orderID
FROM Customers c JOIN orders o
ON c.CustomerID = o.CustomerID
A less complicated answer:
SELECT EmailAddress, OrderID, OrderDate AS OldestOrder
FROM Customers AS C
JOIN Orders AS O1
ON C.CustomerID = O1.CustomerID
WHERE O1.OrderDate =
(SELECT MIN(OrderDate)
FROM Orders AS O2
WHERE C.CustomerID = O2.CustomerID)
Use ROW_NUMBER() to get unique ids for each customer which orders by OrderDate in descending order. And the latest date will be RNO=1. Now do the filtration in outer query.
SELECT EmailAddress, OrderDate, orderID
FROM
(
SELECT ROW_NUMBER() OVER(PARTITION BY c.CustomerID ORDER BY OrderDate DESC)RNO,
EmailAddress, OrderDate, orderID
FROM Customers c JOIN orders o
ON c.CustomerID = o.CustomerID
)TAB
WHERE RNO=1
You can still use HAVING Clause and the IN Operator to achieve same results for this particular problem
Code:
SELECT DISTINCT EmailAddress, OrderID, OrderDate
FROM Customers
JOIN orders
ON Customers.CustomerID = Orders.CustomerID
GROUP BY EmailAddress, OrderID, OrderDate
HAVING OrderID IN (1,2,4,5,6,7,8)
ORDER BY EmailAddress ASC;
I am trying to recap on my sql skill, now I am trying to run a simple query on northwinddb to show me the top customer for each year, but as soon as I use the TOP function only 1 record gets display no matter on what I partition by, This is my T-SQL code
SELECT DISTINCT TOP 1 C.CompanyName
, YEAR(O.OrderDate) AS Year
, SUM(Quantity) OVER(PARTITION BY C.CompanyName, YEAR(O.OrderDate)) AS Total
FROM Customers C JOIN Orders O
ON C.CustomerID = O.CustomerID JOIN [Order Details] OD
ON O.OrderID = OD.OrderID
You can do this bit more compactly in SQL Server 2008 as follows:
select top (1) with ties
C.CompanyName,
Year(O.OrderDate) as Yr,
sum(OD.Quantity) as Total
from Orders as O
join Customers as C on C.CustomerID = O.CustomerID
join "Order Details" as OD on OD.OrderID = O.OrderID
group by C.CompanyName, Year(O.OrderDate)
order by
row_number() over (
partition by Year(O.OrderDate)
order by sum(OD.Quantity) desc
);
Thank you for the help. I found a way that allows me to change the number of top customers i want to see for each year. By using Sub queries and Row_Number
SELECT CompanyName
,yr
,Total
FROM(SELECT CompanyName
, yr
, Total
, ROW_NUMBER() OVER(PARTITION BY yr ORDER BY yr, Total DESC) AS RowNumber
FROM(SELECT DISTINCT CompanyName
, YEAR(O.OrderDate) AS yr
, SUM(OD.Quantity) OVER(PARTITION BY CompanyName
, YEAR(O.OrderDate)) As Total
FROM Customers C JOIN Orders O
ON C.CustomerID = O.CustomerID JOIN [Order Details] OD
ON O.OrderID = OD.OrderID) Tr)Tr2
Where RowNumber <= 1
Three steps: first sum quantities grouped by company and year, then order the results by quantity, then filter first row by group only.
; WITH sums as (
SELECT C.Companyname, YEAR(O.OrderDate) AS Year, sum (Quantity) Total
FROM Customers C JOIN Orders O
ON C.CustomerID = O.CustomerID JOIN [Order Details] OD
ON O.OrderID = OD.OrderID
group by C.Companyname, YEAR(O.OrderDate)
)
with ordering as (
select Companyname, Year, Total,
row_number() over (partition by CompanyName, Year order by Total desc) rownum
from sums
)
select *
from ordering
where rownum = 1