The Bit Bucket

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 you define a column default with code like below:

USE tempdb;
GO

DROP TABLE IF EXISTS dbo.Customers;
GO

CREATE TABLE dbo.Customers
(
    CustomerID int IDENTITY(1,1)
        CONSTRAINT PK_dbo_Customers PRIMARY KEY,
    TradingName nvarchar(100) NOT NULL,
    CreatedDate datetime2(3) NOT NULL DEFAULT (SYSDATETIME())
);
GO

the system will define the name of the default. Can you give examples of why specifying the name of the default instead of letting the system supply it would be a good practice?

2021-04-15

Version 21 of our free SDU Tools for developers and DBAs is now released and winging their way out to our SDU Insiders.

You can find details on the tools here.

If you haven’t been using SDU Tools yet, I’d suggest downloading them and taking a look. At the very least, it can help when you’re trying to work out how to code something in T-SQL.

Along with the normal updates to SQL Server versions and builds, we’ve added the following new functions:

2021-04-14

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:

Consider the following code:

USE tempdb;
GO

DROP TABLE IF EXISTS dbo.Customers;
GO

CREATE TABLE dbo.Customers
(
    CustomerID int IDENTITY(1,1)
        CONSTRAINT PK_dbo_Customers PRIMARY KEY,
    TradingName nvarchar(100) NOT NULL,
    CreatedDate AS SYSDATETIME()
);
GO

INSERT dbo.Customers (TradingName)
VALUES (N'Customer A');
GO

SELECT * FROM dbo.Customers;
GO
SELECT * FROM dbo.Customers;
GO

Will the CreatedDate column return the same value in both SELECT statements?

2021-04-13

There are times when you’re writing in any programming language, that you want to output messages back to the client. In T-SQL, the statement provided for that is the PRINT statement.

PRINT is simple enough to use. You give it a  string to return and it prints that string.

It’s different to the SELECT statement, because the SELECT statement returns a rowset (i.e. a set of rows).

In the main image above, you can see a script with both a PRINT and a SELECT. When that script is executed, two things happen. The output of the SELECT statement is returned in the Results tab in SQL Server Management Studio as below:

2021-04-12

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:

Many applications connect to SQL Server databases with users that are members of the db_datareader and/or db_datawriter roles?

Why should you avoid using those roles?

Answer:

db_datareader and db_datawriter are fixed database roles that were provided for convenience. They aren’t a good option from a security perspective.

2021-04-09

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: Intro

Question:

Many versions of SQL require every SQL statement to be terminated with a semicolon.

Since it was created, T-SQL has listed statement terminators as optional.

Are there any situations where they are required, and not optional?

2021-04-08

I get a lot of book recommendations from friends. One that I’d heard about a number of times was Mark Manson’s book The Subtle Art of Not Giving a F*ck: A Counterintuitive Approach to Living a Good Life so I thought I’d check it out.

I don’t overly love the title. I think having expletives in book titles is a bad omen. For me, they are in the same category as, and are reminiscent of, childhood fart jokes. And the book is full of endless repetition of the same expletives. I can only imagine Manson thought they made for good shock value. For me, they don’t.

2021-04-07

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: Intro

Question:

Look at the following multi-row INSERT statement:

INSERT Sales.CustomerGroups
(
    CustomerGroupID, CustomerGroupName
)
VALUES (1, 'Group A'),
       (2, NULL),
       (3, 'Group C');

The column CustomerGroupName is defined as NOT NULL so the second row cannot be inserted.

2021-04-06

Imagine that I’ve used ROW_NUMBER to number all the cinemas in my database. I’ll get values from 1 to the maximum number of cinemas. But what if I want to number the cinemas within each city? i.e. Aberdeen has three cinemas, so number them 1, 2, and 3. But when we get to the next city, start the numbering again. We can do this by adding PARTITION BY to the OVER clause.

2021-04-05

IT people get accused all the time, of being out of touch with other people, and for using language that is overly complex.

So many times lately, I’ve come across dialog boxes like the one above.

It’s clearly asking a Yes/No question. Why on Earth doesn’t it give the user Yes and No as answer choices?

Why do we do this to users?

If you’re building apps, please don’t do this. If you ask a question that in normal language would lead to a Yes or No response, please give the users Yes and No as answer choices.

2021-04-02