Join (relational algebra)

Okay kiddo, let me explain join in a fun and simple way. Imagine you have a toy box and another friend has a toy box too. You both have different toys in your boxes, but there might be some toys that are the same in both boxes.

Now, if you both want to play together, you might want to see all the toys you have in common. This is exactly what join does in databases!

In a database, you have tables with different information about things like people, products, or sales. All this information is stored in different tables, just like you and your friend’s toys are stored in different boxes.

A join allows you to put these tables together to see the information they have in common, just like when you and your friend put your toys together to see the ones you share.

When you use a join in a database, you pick two tables and tell the computer which columns to look at. The computer then compares those columns and gives you back the information that is the same in both tables.

For example, let’s say you have a table with information about people’s names and addresses, and another table with information about people’s ages. If you want to see the names and ages of people who live in the same city, you could use a join on the “city” column in both tables.

Just like when you and your friend compare your toy boxes, a join helps you see what you have in common. It’s an important tool in databases that lets you combine different sources of information to get a bigger picture of what’s going on.