Sql-Interview

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:

You are writing a script to change the code in a T-SQL function.

You can choose to either DROP IF EXISTS and CREATE the procedure, or to use an ALTER statement.

What advantage would you get from using an ALTER statement?

2025-03-07

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: Medium

Question:

A query included within a stored procedure, has a predicate written like this:

WHERE ISNULL(ProductSize, '') = ISNULL(@ProductSize, '')

A problem has been identified with this predicate. The system needs to be able to differentiate between NULL values for product size and blank strings. Currently both are treated as though they are the same.

2025-02-23

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: Medium

Question:

With SQL Server on-premises, you can create a CREDENTIAL and they are stored in the master database.

What option do you have with Azure SQL Database?

Answer:

You can create a DATABASE SCOPED CREDENTIAL in both SQL Server and in Azure SQL Database.

2025-02-21

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

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

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:

While developers don’t mind adding indexes to a database, most people are very nervous about ever removing them.

Tools let us see whether or not an index is being used, but it’s useful to know why the index was added in the first place.

2025-02-07

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: Administration Level: Medium

Question:

You have two tables:

• dbo.Customers
• dbo.Orders

The dbo.Orders table has a column CustomerID that is declared as a foreign key to the CustomerID column in the dbo.Customers table. In the dbo.Customers table, CustomerID is the primary key.

2025-02-06

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:

You see the following statement in a query that you are reviewing.

What is the purpose of the NULLIF function in this statement?

SELECT @a / NULLIF(@b, 0);

What was the author trying to achieve?

2025-02-05

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:

I execute the following query:

SELECT st.SalesTerritoryID AS [ID],
       st.SalesTerritoryName AS [Name],
       st.DateCreated
FROM dbo.SalesTerritories AS st

UNION

SELECT p.ProductID AS [Product],
       p.[Description],
       p.DateCreated AS [StartDate]
FROM dbo.Products AS p;

What alias will be returned for the each column in the returned results?

2025-02-04

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: Medium

Question:

User1 has CONNECT permission to a SQL Server and is a member of the db_datawriter role in the database Database1.

User2 has CONNECT permission to the same SQL Server and is a member of the db_datareader role in the database Database1.

2025-01-31