How do you concatenate first_name and last_name with a space in between?

• A. SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM employees;
• B. SELECT CONCAT_WS(' ', first_name, last_name) AS full_name FROM employees;
• C. SELECT first_name + ' ' + last_name AS full_name FROM employees;
• D. SELECT first_name || ' ' || last_name FROM employees;

Answer: (A)

Concatenating two name parts with a space between is done by treating the space as its own piece in the concatenation. The expression uses CONCAT with three arguments: first_name, ' ', and last_name, which yields a full name like 'Jane Doe' and the alias names the output column as full_name. This approach is simple and portable across many SQL engines that support CONCAT. Alternative methods exist, such as using a separator function that handles NULLs differently, or using different operators like + or || depending on the database; however, these can be less portable or behave differently with NULLs. So the shown form is a clear, reliable way to get a space-separated full name in most environments.