Scala and Spark for Big Data Analytics

Joins

In traditional databases, joins are used to join one transaction table with another lookup table to generate a more complete view. For example, if you have a table of online transactions by customer ID and another table containing the customer city and customer ID, you can use join to generate reports on the transactions by city.

Transactions table: The following table has three columns, the CustomerID, the Purchased item, and how much the customer paid for the item:

CustomerID	Purchased item	Price paid
1	Headphone	25.00
2	Watch	100.00
3	Keyboard	20.00
1	Mouse	10.00
4	Cable	10.00
3	Headphone	30.00

 

Customer Info table: The following table has two columns, the CustomerID and the City the customer lives in:

CustomerID ...