February 5, 2025
This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around […]
February 5, 2025
One thing you might not have considered is that a table can also be joined to itself. Imagine that I want a list of employees, but […]
February 4, 2025
This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around […]
February 4, 2025
Of course, you might also need to join more than two tables. The example above shows how to do that. I started with the Orders table, […]
February 3, 2025
Our free SDU Tools for developers and DBAs, now includes a very large number of tools, with procedures, functions, and views. A while back, we added […]
February 3, 2025
After discussing LEFT OUTER JOIN, you might wonder if there is also a RIGHT OUTER JOIN. There is, and it’s the reverse of the left one. […]
February 2, 2025
The next type of join that I want to discuss in these posts is a left outer join. We use this mostly, when we know that […]
February 1, 2025
There are two ways you can write common join syntax. There’s an older way to write the query and a new way to write the query. […]
January 31, 2025
The most common form of join between two tables is what’s called an inner join. In the example shown above, I’ve selected some columns from different […]
January 30, 2025
A foreign key is a situation where we store the primary key of one table in another table. It’s very useful. For example, we might need […]
January 29, 2025
In the previous post, we saw how CROSS JOIN operations work. Now it’s rare for us to want to have every combination of the rows in […]
January 28, 2025
The simplest way to join two tables is what’s called a cross-join. So this is where I say from products, cross-join, sales territories. SELECT * FROM […]