If you’re getting an error that reads something like “The objects “employees” and “employees” in the FROM clause have the same exposed names. Use correlation names to distinguish them’” in SQL Server, it could be that you’re trying to do a self-join without assigning table aliases.

When doing self-joins, we need to provide aliases for the tables so that SQL Server can distinguish between each instance.

To fix this issue, be sure to use unique table aliases in your query.

Example of Error

Here’s an example of code that produces the error:

SELECT 
    employees.employee_id,
    employees.first_name AS employee_first_name,
    employees.last_name AS employee_last_name,
    employees.first_name AS manager_first_name,
    employees.last_name AS manager_last_name
FROM 
    employees
LEFT JOIN 
    employees ON employees.manager_id = employees.employee_id
ORDER BY 
    employees.employee_id;

Output:

Msg 1013, Level 16, State 1, Line 1
The objects "employees" and "employees" in the FROM clause have the same exposed names. Use correlation names to distinguish them.

I was doing a self-join but I didn’t provide table aliases for the tables, which caused the issue.

Solution

To fix this issue, we must provide unique table aliases:

SELECT 
    e.employee_id,
    e.first_name AS employee_first_name,
    e.last_name AS employee_last_name,
    m.first_name AS manager_first_name,
    m.last_name AS manager_last_name
FROM 
    employees e
LEFT JOIN 
    employees m ON e.manager_id = m.employee_id
ORDER BY 
    e.employee_id;

Output:

employee_id  employee_first_name  employee_last_name  manager_first_name  manager_last_name
-----------  -------------------  ------------------  ------------------  -----------------
1            Hank                 Blankfield          null                null             
2            Boz                  Whittle             Hank                Blankfield       
3            Mike                 Johnson             Hank                Blankfield       
4            Emily                Fields              Boz                 Whittle          
5            David                Pease               Boz                 Whittle          
6            Sesh                 Lee                 Mike                Johnson          
7            Fitch                Davis               Mike                Johnson         

No error.

In this query I reference the employees table twice in the FROM clause, and so I gave the first one an alias of e and the second one m. Then I used those aliases whenever I referred to columns from the tables. This fixed the error, and the query returned its result as intended.