Subquery SELECT not working properly in SQL Server

Data and Databases
1

I’m having trouble with a subquery in SQL Server and can’t figure out what’s going wrong.

SELECT employee_id FROM (SELECT employee_id FROM staff_records)

This query throws an error but I expected it to work the same way as:

SELECT employee_id FROM staff_records

I thought the inner query would create a temporary result set that the outer query could then use. Am I missing something about how subqueries work in SQL Server? What do I need to fix to make this nested SELECT statement run correctly?

2

SQL Server requires table aliases for derived tables - that’s what’s causing your error. Your subquery creates a derived table, and SQL Server won’t run it without an alias. Here’s the fix:

SELECT employee_id FROM (SELECT employee_id FROM staff_records) AS subquery_alias

This rule is specific to SQL Server and differs from other databases. Without the alias, the parser can’t reference the derived table and throws a syntax error. You can use any valid identifier as the alias.

3

totally get it, sql server can be picky! just add an alias like as t at the end of your subquery, even if you don’t use it. it’s a bit of a pain but that’s how it is. good luck!

4

hmm that’s interesting - you need to give your subquery an alias. Try FROM (SELECT employee_id FROM staff_records) as temp_table or something similar. SQL Server gets confused without knowing what to call that derived table. Have you tried adding the alias? What’s the exact error message you’re getting?