“Intersecting Nuggets for Neighboring Elephants Reunite” - I’ll explain that that means in the article below. It’s a pretty amazing story. But first, a flashback.
I remember my first job interview out of college at an up and coming internet strategy firm during the first dot.com boom and bust years. The person across the table from me was a senior executive at the company but also a super bright guy, and proceeded to test the breadth of my technical prowess. I had a pretty good understanding of all front-end coding, design and strategic concepts but my knowledge of database management, normalization and SQL scripting was rather amateur. (He later told me that he asks this question because it separates the real nerds from the fake ones).
“What is the difference between an inner-join and an outer-join?”
It's not terribly difficult concept, but you need to constantly be using this tactics to explain it in layman’s terms. It's not something that necessarily sticks with you. So I asked ChatGPT to describe it for me.
First, it fed me back a pretty detailed textbook answer that seem to work well:
An inner join and an outer join are two types of operations in database and SQL management that combine data from two or more tables based on a related column. They are used to retrieve information from multiple tables in a single query, but the way they combine the data is different.
**Inner join:**
An inner join returns only the rows from both tables that have matching values in the specified columns. In other words, it retrieves the intersection of the two tables based on the join condition.
Example: Let's say we have two tables - Customers and Orders.
- Customers: (CustomerID, CustomerName)
- Orders: (OrderID, CustomerID, Product)
A simple inner join query looks like this:
```
SELECT Customers.CustomerName, Orders.Product
FROM Customers
INNER JOIN Orders ON Customers.CustomerID = Orders.CustomerID;
```
This query will return the rows where there's a match between CustomerID in both tables, combining the CustomerName and Product information.
**Outer join:**
An outer join returns all the rows from one table and the matching rows from the other table. If there's no match, NULL values are returned for the columns from the table without a match. There are three types of outer joins: left, right, and full.
- Left outer join: Returns all rows from the left table and the matching rows from the right table. If no match, NULL values are returned for the right table's columns.
- Right outer join: Returns all rows from the right table and the matching rows from the left table. If no match, NULL values are returned for the left table's columns.
- Full outer join: Returns all rows from both tables, with NULL values in the columns where there's no match.
Example: Continuing with our Customers and Orders tables, let's see a left outer join query:
```
SELECT Customers.CustomerName, Orders.Product
FROM Customers
LEFT OUTER JOIN Orders ON Customers.CustomerID = Orders.CustomerID;
```
This query will return all rows from the Customers table, and if there's a match in the Orders table, it will combine the Product information. If there's no match, NULL values will appear for the Product column.
Then I asked it: What are some other ways to ask you to explain difficult concepts like these?
Certainly! There are different ways to ask for an explanation of complex concepts. Here are a few examples:
Can you explain this concept in simple terms?
Could you give me an analogy or metaphor to help me understand this idea?
How would you describe this to someone who has no background in the subject?
Can you break down the concept into smaller, more manageable pieces?
Can you provide a real-life example to illustrate the idea?
What is the main idea or takeaway I should understand from this concept?
Could you explain this concept using a story or a scenario?
How would you explain this to a child or someone with no prior knowledge of the topic?
I asked it to do #7 and here’s the story it came back with:
Let's use a story to explain the concept of inner join and outer join:
Once upon a time, in a small town called Datasville, there was a school with many students. Two teachers, Mr. Inner and Ms. Outer, were planning a joint party for their students. They both had a list of students' names and their favorite snacks.
Mr. Inner, the math teacher, was very strict about the party rules. He decided that only students who were on both his list and Ms. Outer's list could attend the party. He compared the lists and invited the students whose names appeared on both lists. He also made sure to serve only the snacks that were favorites of the students attending the party. This approach was like an inner join, where only the common elements (students and snacks) from both lists were considered.
Ms. Outer, the art teacher, was more inclusive. She wanted to invite all the students, regardless of whether they were on both lists or just one. She combined the two lists, inviting everyone, and prepared all the favorite snacks from both lists. If a student's favorite snack wasn't on her list, she just left an empty space on the snack table, like a placeholder. This approach was like an outer join, where all elements from one or both lists were included, and empty spaces (NULL values) were used when there was no match.
In the end, the students enjoyed both parties, but each teacher's approach to organizing the event was different, just like the inner join and outer join concepts in database management.
That’s pretty cool, but now I wondered, is there some memory device I could use to remember which is which?
Yes, you can use a mnemonic device or a memory technique to remember the difference between inner join and outer join. Here's one using the first letters of "inner" and "outer":
**I**ntersecting **N**uggets for **N**eighboring **E**lephants **R**eunite (INNER JOIN)
- Intersecting: Only the common data between tables is selected.
- Nuggets: Represents the shared data points.
- Neighboring: Represents related columns in different tables.
- Elephants: Imagine the tables as elephants that come together to share common nuggets.
- Reunite: Focuses on the shared information between tables.
**O**rganizing **U**niversal **T**ogetherness for **E**lephants **R**egardless (OUTER JOIN)
- Organizing: Represents the process of combining data from both tables.
- Universal: All data from one or both tables is included.
- Togetherness: Represents joining the tables.
- Elephants: Imagine the tables as elephants that join together.
- Regardless: Focuses on including all data points, even if there's no match in the other table.
Visualizing the story of neighboring elephants reuniting and sharing intersecting nuggets for inner join, and organizing universal togetherness for elephants regardless of their differences for outer join, can help you remember the key differences between these two join types.
OK. That’s pretty amazing.
More soon!
A mumbo-jumbo mnemonic to me. Or maybe I am not so intimately into elephants. If that mnemonic appeals to you, I must be a fake nerd, you are the true hard-code nerd. Kudos!
Yeah this is amazing. Sweet times to be alive right?