When creating calculated columns in your Data Warehouse, you will be asked to define a path describing how the table you are creating a column on is related to the table you are pulling information from. To successfully create a path, you need to know two things:
If you know this information, you will be able to easily create a path following the instructions in this article. We have provided an overview of these concepts if you are feeling a little unsure, but you may want to ask a Technical Expert in your organization or reach out to our support team.
We covered this concept in depth in our Understanding and evaluating table relationships article, but a quick summary never hurt anyone, right?
Tables can be related to one another in one of three ways:
||The relationship between people and driver’s license numbers. A person can have one and only one driver’s license number, and a driver’s license number belongs to one and only person.|
||The relationship between orders and items - an order can contain many items, but an item belongs to a single order. In this case, the orders table is the one side and the items table is the many side.|
||The relationship between products and categories: a product can belong to many categories, and a category can contain many products.|
Once a relationship between two tables is understood, it can be used to determine what path should be created to bring information from one table to another. This next step requires knowing the primary and foreign keys that facilitate a table relationship.
Primary Key is an unchanging column or set of columns that produces unique values within a table. For example, when a customer makes an order on a website, a new row is added to the
orders table in your shopping cart, with a new
order_id allows both the customer and business to track the progress of that specific order. Because order id is unique, it is typically the
Primary Key of an
Foreign Key is a column created inside a table that links to the
Primary Key column of another table. Foreign Keys create references between tables, allowing analysts to easy look up and link records together. Let us say we wanted to know which orders belonged to each of our customers. The
customer id column (
Primary Key of the
customers table) and the
order_id column (
Foreign Key in the
customers table, referencing the
Primary Key of the
orders table) allows us to link and analyze this information. When creating a path, you will be asked to define both the
Primary Key and
When creating a column in your data warehouse, you will need to define the path that brings information from one table into another. Sometimes paths pre-populate because a path already exists between tables, but if this does not happen, you will need to create one.
We use the relationship between customers and orders to show you how it is done. Broken down:
one-to-many- a customer can have many orders, but an order can have only one customer. This tells us the direction of the relationship, or where the calculated column should be created. In this case, it means information from the
orderstable can be brought into the
primary keywe want to use is
customers.customerid, or the
customer IDcolumn in the
foreign keywe want to use is
orders.customerid, or the
customer IDcolumn in the
Now, we walk you through actually creating the path.
Click Data > Data Warehouse.
In the table list, click the table you want to create the column in. In our example, it is the
The table schema will display. Click Create New Column.
Give your column a name - for example,
Select the definition for the column. Check out the Calculated Column Guide for a handy cheat sheet.
In the Select table and column dropdown, click the Create new path option.
Using the dropdowns, select the primary and foreign keys for each table.
Many side, we select
orders.customerid - remember, customers can have many orders.
One side, we select
customers.customerid - an order can only have one customer.
Click Save to save the path and finish creating the column.
order_items.order_idcannot point to anything else.
Many-to-manypaths can technically be created, but will very often produce bad data because neither side is a true
one-to-manyforeign key. The best way to approach these paths always depend on the specific desired analysis. Consult the RJ analyst team to uncovering the best solution.
If you are prevented from creating a calculated column due to one or more of the limitations above, contact support with a description of the column you are
Created an incorrect path in your Data Warehouse? Or maybe you are doing a little spring cleaning and want to tidy up? If you need to delete a path from your account, you can send a ticket over to our support analysts. Be sure to include the name of the path!
You should now feel comfortable creating paths for calculated columns in your Data Warehouse. If you are still unsure about a particular path, remember that you can always click Support in your MBI account to get assistance.