Which Transact SQL command executed in Query Analyzer or SQL Server Management Studio returns the version information of the SQL Server instance and the underlying operating system?

Introduction / Context:
Database professionals often need to know exactly which version and build of SQL Server they are working with, along with some basic information about the operating system. SQL Server provides simple ways to retrieve this information using Transact SQL. Interview questions commonly test whether candidates know the command that returns full version details from within tools such as Query Analyzer or SQL Server Management Studio.

Given Data / Assumptions:
We are using Transact SQL commands within SQL Server.The goal is to display version information about SQL Server and the operating system.We are not performing backup, integrity checks, or listing databases in this question.We assume access to a query window where T SQL can be executed.

Concept / Approach:
SQL Server exposes built in functions and commands that return metadata about the instance. The function @@VERSION returns a string that includes the SQL Server version number, build, edition, and brief information about the operating system. This makes it a convenient single line command to use when documenting environments or troubleshooting compatibility issues. Other commands such as sp_helpdb, DBCC CHECKDB, and the BACKUP statement serve very different purposes and do not focus on version reporting.

Step-by-Step Solution:
Step 1: Recall that @@VERSION is a global function that returns the version string for the SQL Server instance.Step 2: Recognize that BACKUP DATABASE is used for backups, not for displaying version details.Step 3: Note that sp_helpdb lists information about databases, while DBCC CHECKDB checks consistency.Step 4: SELECT TOP 1 name FROM sys.databases only returns a database name, not version data.Step 5: Therefore, the correct command to show SQL Server and operating system version information is SELECT @@VERSION, which corresponds to option A.

Verification / Alternative check:
If you open SQL Server Management Studio, connect to an instance, and run SELECT @@VERSION, you will see a text result that includes the product version, build number, edition, and a line indicating the operating system. This practical test confirms the effect of the command. No such output is produced by the backup, help, or DBCC commands listed in the other options, which validates option A as the correct answer.

Why Other Options Are Wrong:
Option B performs a backup of the master database, which is a critical task but unrelated to version reporting and should not be run casually. Option C, sp_helpdb, lists details about each database such as name, size, and status, but not SQL Server build information. Option D, DBCC CHECKDB, checks the integrity of database structures and is used for consistency verification. Option E simply retrieves a database name from sys.databases and does not expose any version or operating system details.

Common Pitfalls:
Some users rely solely on graphical management tools to view version information and forget that a simple query can provide the same details in a scriptable way. Another pitfall is running potentially disruptive commands such as BACKUP or DBCC CHECKDB without fully understanding their impact when trying to inspect a server. Remembering the lightweight and safe SELECT @@VERSION command is a best practice for quick checks.

Final Answer:
The correct answer is: SELECT @@VERSION.