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:

If you pass the following string to SQL Server, will it always reliably be understood as 7th October 2025 by the date, datetime, and datetime2 data types?

'2025-10-07'

If not, why not?

Answer:

No, while that is true for date, and datetime2, the value that will be cast for the datetime data type depends upon the regional settings. For example, in British English, a string in the format ‘XXXX-XX-XX’ will be read as ‘YYYY-DD-MM’.

2025-12-06

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: Administration Level: Medium

Question:

The table dbo.Customers has a clustered index CX_dbo_Customers on the CustomerID column. It also has two non-clustered indexes. One is on the CustomerName column and has an included column of PhoneNumber. The other non-clustered index is on the CityName column.

2025-12-03

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:

You issue the following query against the dbo.Customers table:

SELECT * FROM dbo.Customers;

The table has a clustered index on the CustomerID column.

When you have not specified an ORDER BY clause, which order will the rows be returned in?

2025-11-29

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:

A developer in your team has observed that your database servers are very I/O bound. He thinks the I/O is simply too slow.

What he’s suggesting is that you replace all use of temporary tables with table variables. His argument is that they are memory-based instead of disk-based and that this should help to reduce the I/O load. Your applications make heavy use of temporary tables, and most have large numbers of rows.

2025-11-25

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 are trying to truncate a table but the command is failing.

Can you give some examples of what can cause a truncate command on a table to fail?

Answer:

One common reason is that the table is referenced by a FOREIGN KEY constraint. (But you can truncate a table that has a foreign key that references itself).

2025-10-31

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: Advanced

Question:

You have two SQL Server instances. Each is on a separate virtual machine. Both virtual machines are on the same physical host.

You want to be able to create a transaction that spans both instances of SQL Server. What else needs to be installed?

2025-10-27

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: Advanced

Question:

Several trace flags are in use on a server you manage.

You are concerned that a behavior that you are seeing in a session is being caused by an enabled trace flag. How can you determine which trace flags are enabled for a session?

2025-10-23

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: Administration Level: Medium

Question:

What are mirrored backups?

Do they increase or decrease the reliability of backups?

Answer:

Mirrored backups cause the same backup data to be written to multiple locations.

They decrease the reliability of backups, because if writing to any location fails, all backups fail.

2025-10-19

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:

What are striped backups and why would you use them?

What do they need to be effective?

Answer:

Striped backups cause stripes of the backup to be written to multiple files. This is done to increase performance.

2025-10-15

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: Administration Level: Medium

Question:

You are managing a SQL Server 2022 server and have enabled Instant File Initialization (IFI).

Which files will this apply to?

• Data (MDF and NDF) files only
• Transaction log files only
• Both data and transaction log files

Answer:

2025-10-11