The Bit Bucket

Subqueries allow us to reuse data from one query in another query. There are three basic ways that this can work:

Row sets (tables) - a subquery can return an entire row set with columns. The basic structure of that is shown in the example above.

Lists - a type of row set that has a single column. It’s often used with an IN clause.

Scalar values - a single value returned from a query i.e., one row with one column. These are often used in place of values in expressions or predicates.

2025-02-16

The big week for Down Under podcasts continues. I really enjoyed recording another new Cosmos Down Under podcast this morning. It’s now edited and released.

Show 14 features product manager in the Azure Cosmos DB team Patty Chow.

Patty Chow specializes in open source. She leads the development and strategy for DocumentDB, the open-sourced engine powering vCore-based Azure Cosmos DB for MongoDB. And that’s the key focus for this episode.

2025-02-15

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 SQL Server and Azure SQL Database.

Section: Development Level: Medium

Question:

When writing T-SQL code, you often need to replace NULL values. The core two functions provided are ISNULL and COALESCE.

What is the difference between them?

Answer:

ISNULL only takes a single value to check and replaces it when NULL.

2025-02-15

We saw in previous post that we had a function called GetRecentOrders that gets the most recent orders for a particular cinema.

But what if we want to do that for all the cinemas?

If I’d like the two most recent orders for every cinema, that becomes messy. I can’t just do that with a join, like an inner join or outer join. The function provided is fine. We can use that, but we want to call it for every row in the table.

2025-02-14

Our free SDU Tools for developers and DBAs, now includes a very large number of tools, with procedures, functions, and views. I do a lot of reviewing of database designs and one of my least favourite things to see is the use of default system names for constraints. So we added a tool that can help to find when this has happened. It’s called ListConstraintsWithSystemNames.

The procedure takes three parameters.

2025-02-13

In previous posts, we’ve seen how to query tables. Another type of object that you might need to query is a table-valued function.

Table-valued functions (TVFs) are predefined code i.e., somebody’s written the code, and they take parameters, but they return row set of data, much like a table.

So in the example above, I’m saying I want to declare a Cinema ID variable, and I’ve said let’s have Cinema 27. Then I’ve said I wanted to select from GetRecentOrders. It’s  a TVF that takes two parameters: the Cinema ID, and the maximum number of orders to return. In the case, I’ve said that I want the last two orders for cinema 27.

2025-02-12

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 SQL Server and Azure SQL Database.

Section: Security Level: Intro

Question:

SQL Server can use both logins and users.

What is the difference between them?

Answer:

A login provides access to the server, but not necessarily to any databases.

A user is used to provide access to a database. It might be mapped to a login, but it is possible for databases to authenticate users directly.

2025-02-11

I recently listened to the audio book of Preincarnate by Shaun Micallef.

I need to start by saying that I’m a huge fan of Shaun’s, and I also love hearing him narrate books. Shaun’s humour can be a matter of taste. It’s not for everyone, but I generally love it, although I know many others that don’t. Mad as Hell was one of my favourite TV shows. The one exception is that I wish Shaun would lose the impersonations of Kenneth Williams.

2025-02-10

Another Fabric Down Under podcast is out the door.

This time, the guest was Minni Walia.

Minni is a Principal Program Manager with the Microsoft Fabric Customer Advisory Team (CAT), specializing in the Real-Time Intelligence capabilities within Fabric.

Minni has over 20 years in tech, and has extensive experience in developing applications and data platforms. She spent more than a decade as an Enterprise Architect before transitioning into data analytics and engineering roles at Microsoft.

2025-02-10

Another interesting operator is INTERSECT. We saw how EXCEPT takes a set of rows and removes any duplicates, and removes any rows that are also contained in a second set of rows.

INTERSECT is similar in the way it works, but it only returns the rows that are common to both row sets.

You could replace an INTERSECT statement with a WHERE EXISTS clause but if you need to deal with NULLable columns, and as the number of columns increases, you can see that INTERSECT becomes quite an elegant solution.

2025-02-10