Ok, I hope that my explanation is enough to understand my problem.
We have a company that make some products with determined raw material, this company also sells this raw material but as soon as it gets in the company they have to proceed with some analysis to be sure of the concentration of this material. Ok?
So we can sell some kinds of items, the raw material, the product resultant of the manufacturing of that material, the containers ( bottles, box, envelops ) for that material.
As all these kinds of item have such different information (e.g. a material has expiration date, the container has max ammount supported) we have splitted it into several tables for each type.
Then the inventory control has been separated in some tables that has the static information for each kind such as description, maximum dosis and etc. But I can't find the right way to find the items when it's bought, sold, transformed in other product or even available for selling.
I mean:
If I have two tables (lets say) for products
raw material ( id, description, maximum dosis)
manufactured material ( id, description, )
And a table to deal with the inventory
Inventory (id, analysis_report_id, weight, item_id ( referenced by which of those 2 tables? )
Will I have to use a field for each table and look for which field is filled and then join every product kind table when searching for items in inventory?
I can go more in depth if it stills blurred to understand
(I'm using postgreSQL BTW).
Should I reformulate my question or it is really a complex question?
If I've understood you correctly, I'd factor this into 4 tables:
Item (ItemID, Description, Type)
RawMaterialItem(RawMaterialItemID, maximumDosis, ItemID)
Inventory (id, analysis_report_id, weight, item_id )
The Item table effectively contains all common fields, shared by RawMaterial and ManufacturedMaterial; columns that are unique to Material tables get stored in their own tables, with a foreign key to the Item table. The Type column in the Item table is an indicator of the item type - in your example, it would be either RawMaterial or ManufacturedMaterial.
To get all the data for a given item, you'd look at the type column, and join on the relevant table.
This is pretty ugly - for the alternatives, look at Craig Larman's book "Applying UML and Patterns".
This way, your Inventory table joins to just one table - Item.
Related
I am new to NoSql and DynamoDb, but from RDBMS..
My tables are being moved from MySql to DynamoDb. I have tables:
customer (columns: cid [PK], name, contact)
Hardware (columns: hid[PK], name, type )
Rent (columns: rid[PK], cid, hid, time) . => this is the association of customer and Hardware item.
one customer can have many Hardware Items and one Hardware Item can be shared among many customers.
Requirements: seperate lists of customers and hadware items should be able to retrieve.
Rent details- which customer barrowed which Hardeware Item.
I referred this - secondary index table. This is about keeping all columns in one table.
I thought to have 2 DynamoDb tables:
Customer - This has all attributes similar to columns AND set of hardware Item hash keys. (Then my issue is, when customer table is queried to retrieve only customers, all hardware keys are also loaded.)
Any guidance please for table structure? How to save, and load, and even updates ?
Any java samples please? (couldn't find any useful resource which similar to my scenario)
Have a look on DynamoDB's Adjacency List Design Pattern
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-adjacency-graphs.html
In your case, based on Adjacency List Design Pattern, your schema can be designed as following
The prefix of partition key and sort key indicate the type of record.
If the record type is customer, both partition key and sort key should have the prefix 'customer-'.
If the record is that the customer rents the hardware, the partition key's prefix should be 'customer-' and the sort key's prefix should be 'hardware-'
base table
+------------+------------+-------------+
|PK |SK |Attributes |
|------------|------------|-------------|
|customer-cid|customer-cid|name, contact|
|hardware-hid|hardware-hid|name, type |
|customer-cid|hardware-hid|time |
+------------+------------+-------------+
Global Secondary Index Table
+------------+------------+----------+
|GSI-1-PK |GSI-1-SK |Attributes|
|------------|------------|----------|
|hardware-hid|customer-cid|time |
+------------+------------+----------+
customer and hardware should be stored in the same table. customer can refer to hardware by using
SELECT * FROM base_table WHERE PK=customer-123 AND SK.startsWith('hardware-')
if you hardware want to refer back to customer, you should use GSI table
SELECT * FROM GSI_table WHERE PK=hardware-333 AND SK.startsWith('customer-')
notice: the SQL I wrote is just pseudo code, to provide you an idea only.
Take a look at this answer, as it covers many of the basics which are relevant to you.
DynamoDB does not support foreign keys as such. Each table is independent and there are no special tools for keeping two tables synchronised.
You would probably have an attribute in your customers table called hardwares. The attribute would be a list of hardware ids the customer has. If you wanted to see all hardware items belonging to a customer you would:
Perform GetItem on the customer id. Or use Query depending on how you are looking the customer up.
For each hardware id in the customer's hardware attribute, perform a GetItem on the Hardware table.
With DynamoDB you generally end up doing more in the client application relative to an RDBMS solution. The benefits are that its fast and simple. But you will find you probably move a lot of your work from the database server to your client server.
I have a set of 100 “student records”, I want to have checkboxes for each "favorite_food_type" and "favorite_food", whichever is checked would filter a "bar graph" that counts number of reports that contain that specific "favorite_food"type" and "favorite_food" schema could be:
name
favorite_food_type (e.g. vegetable)
favorite_food (e.g. banana)
I would like to in the dashboard be able to select via checkboxes, “Give me all the COUNT OF DISTINCT students with favorite_food of banana, apple, pear“ and filter graphs for all records. My issue is for a single student record, maybe one student likes both banana and apple. How do I best capture that? Should I have:
CASE A: Duplicate Records (this captures the two different “favorite_food”, but now I have to figure out how many students there are (which is one student)
NAME, FAVORITE_FOOD_TYPE,FRUIT
Charlie, Fruit, Apple
Charlie, Fruit, Pear
CASE B: Single Records (this captures the two different “favorite_food”, but is there a way to pick out from delimiters?)
NAME, FAVORITE_FOOD_TYPE,FRUITS
Charlie, Fruit, Apple#Pear
CASE C: Column for Each Fruit (this captures one record per student, but need a loooot of columns for each fruit, many would be false)
NAME, FAVORITE_FOOD_TYPE, APPLE, BANANA, PINEAPPLE, PEAR
Charlie, Fruit, TRUE, FALSE, TRUE, FALSE
I want to do this as easy as possible.
Avoid Case B if at all possible. Repeating information is almost always best handled by repeating rows -- not by cramming multiple values into a single table cell, nor by creating multiple columns such as Favorite_1 and Favorite_2
If you are provided data with multiple values in a field, Tableau does have functions and data connection features that can be used to split a single field into its constituent parts to form multiple fields. That works well with fixed number of different kinds of information -- say splitting a City, State field into separate fields for City and State.
Avoid Case C if at all possible. That cross tab structure makes it hard to analyze the data and make useful visualizations. Each value is treated as a separated field.
If you are provided data in crosstab format, Tableau allows you to pivot the data in the data connection pane to reshape into a form with fewer columns and many rows.
Case A is usually the best approach. You can simplify it further by factoring out repeating information into separated tables -- a process known as normalization. Then you can use a join to recombine the tables and see the repeating information when desired.
A normalized approach to your example would have two tables (or tabs in excel). The first table would have exactly one row per student with 2 columns: name and favorite_food_type. The second table would have a row per student/favorite food combination, with 2 columns: name and favorite_food. Now each student can have as many favorite foods as you like or none at all. Since both columns have a name field, that would be the key used to join (combine) the tables when needed.
Given that table design, you could have 2 data sources in Tableau. The first one just pointed to the student table and could be used to create visualizations that only involved students and favorite_food_types. The second data source would use a (left) join to read from both tables and could be used to look at favorite foods. When working with the second data source, you would have to be careful about reporting information about student names and favorite food types to account for the duplicate information. So use the first data source when possible. Finally, you could put both kinds of visualizations on a dashboard and use filter and highlight actions to make interaction seamless despite the two sources -- getting the best of both worlds.
I am making an application for a restaurant.
For some food items, there are some add-ons available - e.g. Toppings for Pizza.
My current design for Order Table-
FoodId || AddOnId
If a customer opts for multiple addons for a single food item (say Topping and Cheese Dip for a Pizza), how am I gonna manage?
Solutions I thought of -
Ids separated by commas in AddOnId column (Bad idea i guess)
Saving Combinations of all addon as a different addon in Addon Master Table.
Making another Trans table for only Addon for ordered food item.
Please suggest.
PS - I searched a lot for a similar question but cudnt find one.
Your relationship works like this:
(1 Order) has (1 or more Food Items) which have (0 or more toppings).
The most detailed structure for this will be 3 tables (in addition to Food Item and Topping):
Order
Order to Food Item
Order to Food Item to Topping
Now, for some additional details. Let's start flushing out the tables with some fields...
Order
OrderId
Cashier
Server
OrderTime
Order to Food Item
OrderToFoodItemId
OrderId
FoodItemId
Size
BaseCost
Order to Food Item to Topping
OrderToFoodItemId
ToppingId
LeftRightOrWhole
Notice how much information you can now store about an order that is not dependent on anything except that particular order?
While it may appear to be more work to maintain more tables, the truth is that it structures your data, allowing you many added advantages... not the least of which is being able to more easily compose sophisticated reports.
You want to model two many-to-many realtionships by the sound of it.
i.e. Many products (food items) can belong to many orders, and many addons can belong to many products:
Orders
Id
Products
Id
OrderLines
Id
OrderId
ProductId
Addons
Id
ProductAddons
Id
ProductId
AddonId
Option 1 is certainly a bad idea as it breaks even first normal form.
why dont you go for many-to-many relationship.
situation: one food can have many toppings, and one toppings can be in many food.
you have a food table and a toppings table and another FoodToppings bridge table.
this is just a brief idea. expand the database with your requirement
You're right, first one is a bad idea, because it is not compliant with normal form of tables and it would be hard to maintain it (e.g. if you remove some addon you would need to parse strings to remove ids from each row - really slow).
Having table you have already there is nothing wrong, but the primary key of that table will be (foodId, addonId) and not foodId itself.
Alternatively you can add another "id" not to use compound primary key.
I have created an adaptation of the 'Goods' database that includes a quote feature. The user selects the customer (customer table), Product (product table), qty, discount ect.
The chosen entities then get saved to the quotes table and there is a 'print' function on form.
Whilst the information can be saved and the quote prints via a quote report, I'm having major difficulty in finding a way to add multiple products to a single quote.
The main objective is to be able to select various products and add their total price (product after addition of qty, discount) to a SUB TOTAL
Quote total is therefore the formula Tax+Shipping+SubTotal
any takers? :)
Hi guys,
Thanks for the response I really appreciate it. As for tax and shipping, they are just added in the form and are not pushed from anywhere else in the database. Its simply a type in form and display on report sort of thing. As you said in the answer, HansUp, the salesperson will compute it seperately and just input it.
As for tax, products will be shiped globally so the tax/vat shall be computed seperately also.
Also, each table DOES have its own unique ID.
More to the point of having QuoteProducts. I can't seem to get my head around it! Are you saying that whatever products are chosen in QuoteProducts will create a QuoteProd_ID and then that ID's total price will therefore be added to the Quote?
I tried making a subform before but through the 'multiple records' form but obviously every selection made its own ID. Is there any way you could elaborate on the Quote products part and how it allows multiple records to store to one ID? Without understanding it i'm pretty much useless.
In addition, how the multiple records are then added up to make the subtotal also baffles me. Is that done in the Quote form?
Edit 2
HALLELUJAH.
It works! I created a sum in a textbox on the footer of the subform and then pushed that into subtotal :)
I do have one slight issue:
I made a lookup&relationship for the ListPrice. I don't think its the correct way to do it as it comes up with the price of every light (i.e 10 products priced £10, £10 shows up ten times in dropdown).
Can you guys help?
List Price Problem
here's what i've tried:
1) Create >Client>Query Design
2) Show Products, QuoteDetails. For some reason, it automtically comes up with ListPrice, ProductID (as it should) and Product Name linked to ID in Products
3) Delete links with ListPrice and ProductName.
4) Show all in quoteDetails (*)
5) Create Multiple Items form
Doesnt work! What am I doing wrong?
I'm extremely grateful for both your help. If I can do anything, just shout.
Ryan
In addition to HansUp's stellar answer, you might be interested in DatabaseAnswers.org. They have a number of data models for free that might provide additional insight to your situation and possibly serve as inspiration for future projects you may encounter.
Edit 1
Forget about the form and report for a moment - they are important but not as important as the data and how you store the data.
In your current design, you have a quotes table presumably with an autonumber key field. For the purposes of this answer, this field is named Quote_ID.
The quotes table, as HansUp suggested, should store information such as the Customer_ID, Employee_ID, OrderDate and perhaps even a reference to a BillingAddress and ShippingAddress.
The quotes table SHOULD NOT store anything about the products that the customer has ordered as part of this quote.
Instead, this information should be stored in a table called QuoteProducts or QuoteDetails.
It's structure would look something like the following:
QuoteDetails_ID --> Primary Key of the table (autonumber field)
Quote_ID --> Foreign key back to the Quotes table
Product_ID --> Foreign key back to Products table
Quantity
UnitPrice
You may also want to consider a field for tax and a separate field for shipping per line item on the quote. You will inevitably run into situations where certain items are taxable in some locations and not others, etc.
This design allows a particular quote to have any number of products assigned to the quote.
Returning to your form \ reports, you would need to change your existing forms and reports to accomodate this new table design. Typically one would use a main form for the quote itself, and then a subform for the quote details (item, price, quantity, etc).
To get the quote total, you would sum the items in QUoteDetails for a particular Quote_ID.
You may also want to check out the Northwind sample database from Microsoft. From what I recall Northwind had a sample Orders system that might help make these ideas more concrete for you by seeing a working example.
For the first 3 tables mentioned in your comment, each should have a primary key: Customers, customer_id; products, product_id; and employees, employee_id.
The quotes table will have its own primary key, quote_id, and will store customer_id and employee_id as foreign keys. (I'm assuming you want employee_id to record which customer representative/salesperson created the quote.) You may also decide to include additional attributes for each quote; date and time quote prepared, for example.
The products offered for quotes will be stored in a junction table, QuoteProducts. It will have foreign keys for quote_id and product_id, with one row for each product offered in the quote. This is also where you can store the attributes quantity and discount. An additional field, unit_price, can allow you to store the product price which was effective at the time the quote was prepared ... which would be useful in case product prices change over time. I don't know whether tax should be included in this table (see below).
I also don't know how to address shipping. If all the products associated with a quote are intended to be delivered in one shipment, shipping cost could be an attribute of the quotes table. I don't know how you intend to derive that value. Seems like it might be determined by shipping method, distance, and weight. If you have the salesperson compute that value separately, and then input the value, consider how to handle the case where the product selection changes after the shipping fee has been entered.
That design is somewhat simplistic, but might be sufficient for the situation you described. However, it could get more complex. For example, if you decide to maintain a history of product price changes, you would be better off to build in provisions for that now. Also, I have no idea how tax applies in your situation --- whether it's a single rate applied to all products, varies by customer location, varies by type of customer, and/or varies by product. Your business rules for taxes will need to be accommodated in the schema design.
However, if that design works for you (test it by entering dummy data into the tables without using a form), you could create a form based on quotes with a subform based on QuoteProducts. With quote_id as the link master/child property, the subform will allow you to view all products associated with the main form's current quote_id. You can use the subform to add, remove, and/or edit products associated with that quote.
Not much I can say about the report. There is a lot of uncertainty in the preceding description. However, if your data base design allows you to build a workable form/subform, it should also support a query which gathers the same data. Use that query as the record source for the report. And use the report's sorting and grouping features to create the quote grand total.
Edit: With the main form/ subform approach, each new row in the subform should "inherit" the quote_id value of the current record in the main form. You ensure that happens by setting the link master/child properties to quote_id. Crystal Long explains that in more detail in chapter 5 of Access Basics by Crystal: PDF file. Scroll down to the heading Creating a Main Form and Subform on page 24.
Edit2: Your strategy may include storing Products.ListPrice in QuoteDetails.ListPrice. That would be useful to record the current ListPrice offered for a quote. If so, you can fetch ListPrice from Products and store it in QuoteDetails when you select the ProductID for a row in the subform. You can do that with VBA code in the after update event of the control which is bound to the ProductID field. So if that control is a combo box named cboProductID and the subform control bound to the QuoteDetails ListPrice field is a text box named txtListPrice, use code like this for cboProductID after update:
Me.txtListPrice = DLookup("ListPrice", "Products", "ProductID = " _
& Me.cboProductID)
That suggestion assumes the Products and QuoteDetails tables both include a ProductID field and its data type is numeric. And cboProductID has ProductID as its bound field and uses a query as its RowSource similar to this:
SELECT ProductID, ProductName
FROM Products
ORDER BY ProductName;
I have a Product table and a ConfigurableProduct table.
If there are several variations of the same product like a shirt in different colors I create a ConfigurableProduct.
When a user is looking at the catalog he should see a list of products unless there is a ConfigurableProduct, then he should see it with a select box for each variations.
How do I structure the tables for Product and ConfigurableProduct and how do I query the db so I can page through the results?
Thanks
I am going to answer this as if you do not have tables created. I am not sure if that is true though.
The following is a simple example, but I assume you have more data.
products
id
name
configurable_products
id
variation
product_id REFERENCES products(id)
You can just make the configurable products a reference to products.
If you want a listing of products with their configurations then you can do:
select p.name, c.variation
from products p left outer join configurable_products c
on (p.id = c.product_id);
Of course you can just search for all the configurable_products based on the product id too when needed.
As for the paging part of your question you will have to clarify what you mean. You can use limit to limit results if you don't want to get everything at once.