I have a model where a Shipment can have many Products through a product_shipments lookup table.
The Shipment model also has a relationship where a shipment can have one to many bill_of_lading numbers.
Is it proper to create a new table for just one bill_of_lading field ? Most cases a shipment will have only one bill_of_lading number, but often a shipment will contain 2 or more.
There are no other attributes for a bill_of_lading that need to be tracked other than just the number.
What is the proper way to handle this case?
Normalization rules would suggest pulling this out into its own table , correct ?
Yes, I would suggest you to do the same thing as you did with Shipment and Products, i.e. create new table. It is a proper way of doing it and easier for you to query later on and even altering your table structure should you need to.
Well, it wouldn't have one column, it would have two... a shipment ID and a bill_of_lading number. It could be correct to have a table with just those two fields. It could also be correct to create a field with bill_of_lading, shipment, and product if you can explicitly divide the products into individual bills of lading. It depends really on the relationship between bill_of_lading and product.
Related
I found a schema in Google Images (see below) that can illustrate a problem I having in my data warehouse design:
My design is different, but this is the simplest figure I could find to convey my question, which is given the figure, I'm wondering how could the schema accommodate the following scenario: if a product had a unique number assigned to it by the SalesOrg (salesOrg_product_number)...For example, a salesOrg sells food items and assigns all food items of the same kind the same unique salesOrg_product_number. A different salesOrg would have a different salesOrg_product_number for that type of product.
I'm inclined to place the salesOrg_product_number attribute in the Product dimension table, but part of me thinks it should be in the salesOrg dimension table instead. I'm wondering which one of these is correct way in a data warehouse (not relational db) design to maintain the star schema?
In a perfect world the Primary Keys of a dimension table should be just surrogate key, without any meaning for the business. Table IDs should be invisible for the final users, but business code should be of course available.
A possible solution would be to have a product table with a structure like:
Product_id
Product_desc
Product_SO1_number
Product_SO2_number
...
Of course this will require to show the correct field to the correct Sales Organization. Depending on your reporting tool this can be more or less difficult. For example if you write your query manually you need just to put the right column in your select.
Another possibility would be to have a product/sales_org table, a table which combine the Product and the Sales_Org one:
Product_Sales_Org_id
Product_id
Sales_Org_id
Product_SO_number
...
This table will be child of the two dimension table and on the fact table you will have Product_Sales_Org_id column. Depending on Product and Sales Organization the Product_SO_number will return the correct number per SO.
If you want to have this in a star schema structure you can put Product/Sales_Org/Product_Sales_Org together in only one table like:
Product_Sales_Org_id
Product_id
Sales_Org_id
Product_desc
Sales_Org_desc
Product_SO_number
...
Sincerely I would go for the second solution, keep the Product and the Sales_Org tables separated, because they are two different business entities and implement the relationship table in the middle.
I hope this helps.
It might be a stupid question, but here goes:
Is it possible to make a dynamic table that's able to contain rows with variable number of columns and custom column names?
I have glanced over EAV-modelling, but it seems heavy. A real life example could be this:
Let's say I have a register with customers. But each customer might have different information to be entered. And depending on what you want to enter, it should be reflected in the database. (I.E. every customer has different columns)
Is this impossible/probable?
Update:
The standard approach (i.e. having a table with all needed columns and saving information only into columns that make sense for a particular customer while setting the remaining ones to NULL) doesn't work for me because what I want can't use 'fixed' column names. Example one customer might want CVR-number and another might want their phonenumber as a reference number. And a third might want some completely different information. So to avoid having a table containing 500 columns, I have now thought of making an extra table containing rows of column-data. Like so: Id, Name, Value, CustomerId. So when I want information for a customer, all I have to do is to iterate through this table with a specific customer Id.
my own edit!:
Sorry for troubling you with this simple SQL-issue! :-) Have a nice day...
You could model this as a one-to-many relationship between a Customer and a CustomerAttributes table. Something like:
**Customer table**
CustomerId
LastName
FirstName
...
**CustomerAttributes table**
CustomerId
AttributeName
AttributeValue
This is not possible in Sql-Server. As Marco says, you can store each customer's data in xml.
If all the columns are known ahead of time and some customers use one set and other customers use a different set, then sub-tables with each set of columns is the normal approach.
If the columns are not known ahead of time, then how would the data even be used? No code or reports could refer to it. Perhaps it should be stored unstructured in a general purpose 'Notes' field.
As far as I know it's not possible in standard relational databases, but you can take a look at schema-less databases called 'No-SQL' like MongoDB
I have a table for the "Features and benefits" of a list of products. In this table there is an item number, base part number, and three benefit columns. I want to change this to a dynamic table in which they can have any number of benefits, which I can do easily. The problem is the features and benefits do not change between items under the same base part number. For example under the base part "708" the items 708/s, 708/m and 708/l would all have the same features and benefits, so I want to get rid of the redundancy by removing the item column and just have a single entry for each distinct base part number. How would I go about this?
You might need to introduce a 'benefits grouper' field in your table, and relate that to another table with benefitsGrouperID, benefitSequence, and benefit
Maybe I need more coffee this morning but here goes...
I have a very simple inventory system. Right now I have two tables: Items and Inventory.
Items
Id
Title
YearReleased
Inventory
Id
ItemId(Foreign key to Items)
Quantity
QuantityOnHand
Each item has one inventory and each inventory belongs to one item. The relationship between the two is one-to-one. However, when I diagram this out, the relationship based on my setup thus far is a one-to-many, due to the auto-incrementing id I have for Inventory.
Now, I could make this one-to-one by eliminating the auto incrementing id in the Inventory table, but this makes me feel dirty. I always use internal id's for primary keys.
I see a few options:
1.) Remove the auto incrementing id field in Inventory and live with the dirty feeling.
2.) Keep the tables as-is.
3.) Merge Items and Inventory into one table: ItemsInventory.
4.) Something else?
If your relationship is really one to one, drop the Id from the Inventory table and use ItemId as PK and FK. Also, name both keys ItemId -- helps.
If you're certain that the mapping will always be 1:1, then merge the two tables into one.
However, are you certain that the relationship will allways be 1:1?
Since many ORMs require a single auto-increment PK, I would:
4) Add a unique index to Inventory.ItemId and it should show as a one-to-one relationship.
Would making ItemId have a constraint to be unique be insufficient? That seems to satisfy your requirements.
If what the table structure you have mentioned is going to remain as it is now, then I think you should merge Items and Inventory into one table: ItemsInventory.
For such small tables it doesn't make sense to partition them vertically. That way you would remove an extra join. Select on a single table is always faster then joins.
I would merge the two tables together my main reason is you will have duplicate data as
well as unnecessary data if you stick with two tables. Querying will also be faster! Looking at the two tables I would merge into one for sure.
Items
Id
Title
YearReleased
Inventory
Id
ItemId(Foreign key to Items)
Quantity
QuantityOnHand
You will have two less collumns full of data if you merge to one table ("ID" ItemID" can be dropped). Writing your logic to retrive and send data to the database will also be easier for you.
I would have this table:
**ItemsInventory**
Id
Title
YearReleased
Quantity
QuantityOnHand
However you must be sure it is a one-one otherwise you may have give yourself a lot of work if the bussiness needs change.
Simon
If you really want to make it a simple inventory system, then merge the tables.
Reasons not to merge the tables/it doesn't stay simple.
How many items will NOT have an inventory record? Your example only shows a few inventory fields and maybe that's all it would ever have. But it the fields you track in inventory grow and there is a large part of items not in inventory, you're going to have a lot of null fields.
How often will inventory get updated? If these fields are a result of other transaction tables (purchases and sales) being updated frequently, no reason to constanatly update the items table just because inventory was purchased or sold. In your current system, users are expecting these values to be real time (If not then they know what isn't up to date since they didn't make the changes.).
I have a doubt regarding a database design, suppose a finance/stock software
in the software, the user will be able to create orders,
those orders may contain company products or third-party products
typical product table:
PRIMARY KEY INT productId
KEY INT productcatId
KEY INT supplierId
VARCHAR(20) name
TEXT description
...
but i also need some more details in the company products like:
INT instock
DATETIME laststockupdate
...
The question is, how should i store the data?
I'm thinking in 2 options:
1 -
Have both company and third-party, products in a single table,
some columns will not be used by third-party products
identify the company products are identified by a supplier id
2 -
Have the company products and third-party in separated tables
3 - [new, thanks RibaldEddie]
Have a single product table,
company products have additional info in a separated table
Thanks in advance!
You didn't mention anything about needing to store separate bits of Vendor information, just that a type of product has extra information. So, you could have one products table and an InHouseProductDetails table that has a productId foreign key back to the products table that stores the company specific information. Then when you run your queries you can join the products table to the details table.
The benefit is that you don't have to have NULLable columns in the products table, so your data is safer from corruption and you don't have to store the products themselves in two separate tables.
Oooo go with 3! 3 is the best!
To be honest, I think the choice of #1 or #2 are completely dependent upon some other factors (I can only thing of 2 at the moment):
How much data is expected (affecting speed of queries)
Is scalability going to be a concern anywhere in the near future (I'd guess within 5 years)
If you did go with a single table for all inventory, then later decided to split them, you can. You suggested a supplier identifier of some sort. List suppliers in a table (your company included) with keys to your inventory. Then it really won't matter.
As far as UNION goes, it's been a while since I've written raw Sql - so I'm not sure if UNION is the correct syntax. However, I do know that you can pull data from multiple tables. Actually just found this: Retrieving Data from Multiple Tables with Sql Joins
I agree with RibaldEddie. Just one thing to add: put a unique constraint on that foreign key in your InHouseProductDetails table. That'll enforce that it's a one-to-one relationship between the two tables, so you don't accidently end up with two InHouseProductDetails records for one product (maybe from some dataload gone awry or something)
Constraints are like defensive driving; they help prevent the unexpected...
I would advice on using point #1. What happens when another supplier comes along? It's also more easy to extend on one product table/produst class.
Take into account the testing of your application also. Having all data in one table raises the possible requirement of testing both the 3rd Party & Company elements of your app for any change to either.
If you're happy that your Unit test would cover this off its not so much of a worry... if you're relying on a human tester then it becomes more of an issue when sizing the impact of changes.
Personally I'd go for the one products table with common details and separate tables for the 3rd party & Company specifics.
one table for products with a foreign key to the Vendor table; include your own company in the Vendor table
the Stock table can then be used to store information about stock levels for any product, not just yours
Note that you need the Stock table anyway, this just make the DB model more company-agnostic - so if you ever need to store stock level information about third-party products, there's no DB change required