Combining Data

Question 1

What are the Benefits of Combining Data?

Answer 1

1. Complete & comprehensive view of a situation = better understanding & accurate analysis 🪟
2. Broader range of data so organisations can make more informed decisions 🏌️
3. Processes streamlined as data accessed from one place 🏞️

Question 2

What are the risks of Combining Data?

Answer 2

1. DQ = sources have different formats = inconsistencies 💾
2. Different terms for the same concept leading to inaccuracies 📖
3. Risk of data breaches ⚠️

Question 3

What is a Full Outer Join?

Answer 3

includes all rows from both tables, regardless of whether there is a match, populating non-matches with nulls

Question 4

Why did you use a Full Outer Join? What are the Benefits?

Answer 4

1. I needed to identify rows present in one table but not another (using NULLS)
2. Ensured no data is lost from both tables
3. A left join would only keep alfabet apps and see if they were logged in Collibra (matches), but I needed both to raise to stakeholders

Question 5

What are the risks of a Full Outer Join?

Answer 5

1. Creates a large data set (storage/processing issues) - not an issue for my Project as datasets were small
2. Introducing NULL values can be challenging to process (changed to a cross to help this)

Question 6

What is a Right Join?

Answer 6

displays rows from the right table along with any rows matching from the left table, showing null values when there is no match

Question 7

What is a right join good for?

Answer 7

focusing on data from the right table while adding insights from the left table

Question 8

What is a left join?

Answer 8

all rows from the left table are included with any matching rows from the right table. NULL values used if there is no match found in the right table

Question 9

What is a disadvantage of a left join?

Answer 9

And other types!
* Impact on performance when scanning for matching rows - time consuming
* Compare apps added to Collibra but not Alfabet to alert stakeholders outside the project
* Therefore Left Join was not suitable

Question 10

What is an inner join?

Answer 10

• Combines rows from multiple tables
• Connecting them through a related column
• Only including rows with matching values
• E.g. apps found in both Alfabet and Collibra
• Rows without matching ID’s would have been excluded

Question 11

What is a benefit of an inner join?

Answer 11

1. Simple ➖ straight forward 📏
2. Great for large data sets, filtering out matching rows 🔍🃏🃏to improve analysis efficiency

Question 12

What is a disadvantage of an inner join?

Answer 12

1. data loss risk since
2. Did not bring back all rows from both tables, so would not work for my use case

Question 13

What is a join?

Answer 13

combines 2 or more datasets based on a common column or key allowing data to be retrieved and analysed together