I have the following schema:
customer(cid,cname),
books(isbn,price)
orders(oid,cid,isbn,odate,quantity,value)
1. A customer can purchase any no.of books on a single order on the same date
2. A customer can purchase any no. of different types on a single orders
3. A customer can place multiple orders on a same day
So, when a customer place order for isbn say 121,141 whose prices are 500,500 respectively, of quantity 2,5 respectively, the column 'value' must be filled with 1*500=500 and 5*500=2500 respectively.
So the value column must be quantity*price always. How can I specify this during the creation of orders table? Should I need a trigger?
I think there is a problem with your model: your orders table refers to the books table via the isbn field, when an order can contain several books !
I would add an intermediate table:
single_order(sid, oid, isbn, quantity)
referring to the orders one via the oid field. An item of orders would then be the sum of the items of single_order having the corresponding oid. And the value field would then be the sum of the price of books by the quantity of single_order, you can easily link to these 2 tables with joins.
Related
I am writing a SQL query that needs to show the total number of orders from each store. The issue I am running into, is that while I can figure out how to sum the orders by product and each product is only sold by one store, I can't figure out how to total the orders by store alone
This is the code I currently have
SELECT storeID AS [STORE], Product_ID
, SUM(quantity) AS [ORDERS BY STORE]
FROM Fulfillment, Store
GROUP BY storeID, Product_ID;
This line of code leads to a repeat of storeID in the results, where ideally, I would only want storeID to be included in the results once with the total quantity of all of Product_ID being included. I tried to remove Product_ID from the GROUP BY statement, but this resulted in the following error
Column 'Fulfillment.Product_ID' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.
I'm new to SQL and am trying to learn, so any help and advice is greatly appreciated
#ZLK is correct that if your goal is a total number of units ordered ("quantity") of any product, simply remove the [product_id] column from the SELECT and GROUP BY.
However, it appears that you're referencing two tables ("FROM Fulfillment, Store") and not specifying how those tables are joined, creating a cartesian join - all rows in one table will be joined to all rows in the other table. If the [storeID] and [quantity] fields are available in the Fulfillment table, I recommend removing the Store table reference from the FROM clause (so "FROM Fulfillment" alone).
One last note: You mention that you want to count "orders". In some circumstances, an order may have multiple products and a quantity > 1. If your goal is the total number of "orders" regardless of the number of products or quantity of products on an order, you'll want to use "COUNT(DISTINCT orderID) as [Orders]" (where "orderID" is the reference to the unique order number).
I'm trying to build a price comparison database with n products and a definitive but changing number of vendors that sell these products.
For my price comparison database, I need to store both current prices for a product across different vendors and historical prices (one lowest price).
As I see it, I have 2 options to design the database tables:
1. Put all vendor prices into the main table.
I know how many vendors there will be and if I add or remove a vendor I can add or remove a column.
Historical prices (lowest price on certain date across all vendors), goes into a separate table with a product name, a price and a date.
2. Have one table for products and one table for prices
I will have only the static attribute data in the main table such as categories, attributes etc and then add prices to a separate product table where I store price, vendor, date in it and I can store the lowest price as a pseudo-vendor in that table for each date or I can store it in a separate table as well.
Which method would you suggest and am I missing something?
You should store the base data in a normalized format that contains all the history. This means that you have tables for:
products, with one row per product and the static information about the products.
vendors, with one row per vendor and the static information about the vendor.
prices, with one row per price along with the date and product and vendor.
You can get the current and lowest prices using a query, such as:
select pr.*
from (select pr.*, min(price) over (partition by product) as min_price
row_number() over (partition by product, vendor order by price_datetime desc) as seqnum
from prices pr
where pr.product_id = XXX
) pr
where seqnum = 1;
For performance, you want an index on prices(product, vendor, price_datetime desc).
Eventually, you may find that this query runs too slowly. In that case, you will then consider optimizations. One optimization would simply be storing the latest date for each price/vendor combination using a trigger, along with the minimum price in the products table -- presumably using triggers.
Another would be maintaining a summary table for each product and vendor using triggers. However, that is probably not how you should start the endeavor.
However, you might be surprised at how well the above query can perform on your data.
I have a list of my stock in one table, stock, and I reserve portions of that stock to an order in another table, orders
I have a feeling my data is no longer in a good state, and I need to compare the amount I have reserved from a chunk of stock in the orders table to the total I have in the reserved stock table.
Each stockref has a unique entry in stock but can occur multiple times in orders if it represents a quantity that is split across multiple orders.
The ideal query would show me stockrefs that are over-reserved. Once I have these I can then check my code to see what caused the issue and fix it before I go bust selling items I no longer have stock of.
I think this should resolve your problem
Select s.reservedqty,s.stockref,O.Total_reservedqty from stock S join
(
Select sum(reservedqty) as Total_reservedqty,stockref from orders group by stockref
) O
On S.stockref=O.stockref
where O.Total_reservedqty !=s.reservedqty
I am helping someone build a grocery deliver service. Very simple site and order process. The problem I am having is knowing how to come up with schema for the orders. The order would have contact information, but would also need to have all of the products they ordered. Since it can/will be different for each persons order, how would I go about designing this? Would I just have a products ordered field with a string list of all the items? Or would I need multiple linked tables?
Thanks!
You need three tables:
a) Products - Contains the product details
b) Orders - Contains the order header, contact information etc
c) Product_Orders - is a table with two columns: product_id and order_id, that bind the orders to the products, and a quantity field and unit price.
You could have a customers table, but ideally information like the delivery address, etc, would be attached to the order so that if the user changes his address it will not affect your order history.
For the same reason unit price must be in Product_Orders, so that if a product price changes it does not affect previous orders.
Product table
with name and price of all products.
Customer table
with name, address, phone etc...
Order table
with entries for each order: order id, cusomer id, date etc
Order Items table
with all ordered items, with link to id in ordertable, product table, quantity, price, etc...
I have two parent child tables and a couple of supporting tables. I am struggling to figure out the right relationships between them.
Orders, a table that holds a list of Orders including:Order Id, Supplier, Order Date etc..
OrderDetails, a Table holds a list of products that have been ordered, and is a child of Orders, linked on OrderId. Key fields are the ProductId and the Quantity Ordered. Each order containes one or many OrderDetails that outline the products and quantities being ordered.
Shipments, a table that holds a list of Shipments, including Tracking Number and Shipper. Links to Orders through Order Id. An Order may have multiple shipments. For example, I ordered 100 lightbulbs. They were dispatched in 5 shipments.
ShipmentDetails, holds a list of product and shipped quantities and is linked to the Shipments table by ShippingId. Each Shipment may have multiple ShipmentDetails. i.e. One shipment may have 30 Lightbulbs and 10 Door Knobs.
Products is a table that holds a list of Products that need to be both ordered and shipped.
So the logic is that I enter details about the products that are to be ordered in Products. For example, 100 CREE LED Lightbulbs, and 50 Door Handles.
When I place an order, I create an Order in Orders.
i.e. amazon.com, order #45454.
Then I add child rows to that order in OrderDetails. i.e. 30 CREE LED Lightbulbs.
When the order Ships, I create an entry in the Shipments table. i.e. Tracking #46464646464, linked to OrderId in Orders. And then I enter what is in that shipment in ShipmentDetails. For example, only 20 or the 30 CREE LED Lightbulbs may be associated with this Shipping entry.
I am struggling with figuring out how to relate the Shipping Detail records to the Order Detail Table. Lets say the Shipping Detail Table has 4 fields.
ShippingID - a link to the Shipments table parent.
TrackingNum - a field that holds a tracking number.
Product - this should be a drop down, that says, the shipment I belong to is related to a defined Order (because ShipmentDetail is a child of a Shipment record which in turn holds a key to the Orders table, which in turn has OrderDetails that reference products).
Quantity - this should have a default (overridable) value that is the "Quantity Ordered" number from the OrdersDetail record that matches the Order Id and Product Id. Where OrderId is in the Shipments table (linked to the Orders table) and ProductID comes from #3 above. The reason it must be overridable is that a shipment may be a partial shipment.
I am stuck with the preceding #3 and #4. I hope I have explained this in a vaguely understandable way! The pictures below may help!
The ask:
What is the correct join between the ShipmentDetails and the OrderDetail Table
How do I create a field in the ShipmentDetail table with a default value pulled from the Quantities Field of the OrderDetail table, where
Shipments!OrderId = Orders!Id and ShipmentDetail!ProductID = OrderDetails!Product ID
I am working in MS Access 2016 - but I suspect this is a fairly generic SQL question...rather than MS Access specific.
I think the naming is confusing.
What I would rather have is (each first id is autoincrement, forgot how to say this on access):
// Product doesn't contain any information about quantity/price etc ...
create table Products(product_id int, name text, description text ...);
// Orders:
create table Orders(order_id int, client_name text, description text ...);
create table OrderDetails(order_detail_id int, order_id int, product_id int, quantity double, unit_price double, ...);
// Shipments
create table Shipments(shipment_id int, company text, description text ...);
create table ShipmentDetails(shipment_detail_id int, shipment_id int, product_id int, quantity double, price double default 0, ...);
// inserting shipments per product (defaulting to total quantity per product), assuming we have shipment_id SID
insert into ShipmentDetails(shipment_id, order_id, product_id, quantity)
select SID, order_id, product_id, SUM(quantity)
from OrderDetails
group by order_id, product_id;
Then you can of course have some filters (date, customer etc ...).
For the first question, I am not clear what exaclty you want to return.
Here is a comparison of quantities:
select t.order_id, t.product_id, sum(t.quantity) as product_quantity, sum(u.quantity) as shipment_quantity
from OrderDetails t inner join ShipmentDetails u
on t.order_id = u.order_id and t.product_id = u.product_id;