Unique Employee ID
Apple
Problem Statement
Large organizations often manage multiple identity systems. You are tasked with generating a report that maps every employee to their unique identifier, if one exists in the secondary system.
Write an SQL query to show the unique ID of each user. If a user does not have a unique ID, display null instead.
Rules:
- The result should include the unique_id and the name of the employee.
- Every employee present in the Employees table must appear in the output.
- The order of the results does not matter.
Tests your understanding of
Basic SQL, Joins, LEFT JOIN and NULL Handling
Input Tables
employees
| id(INTEGER) | name(VARCHAR) |
|---|---|
| 1 | Alice |
| 7 | Bob |
| 11 | Meghan |
| 90 | Winston |
| 3 | Jonathan |
| 4 | Sarah |
employee_uni
| id(INTEGER) | unique_id(INTEGER) |
|---|---|
| 3 | 101 |
| 11 | 102 |
| 90 | 103 |
Expected Output
| unique_id(INTEGER) | name(VARCHAR) |
|---|---|
| null | Alice |
| null | Bob |
| 102 | Meghan |
| 103 | Winston |
| 101 | Jonathan |
| null | Sarah |
Tags
EasyBasic SQLJoinsLEFT JOINNULL Handling
5-10 min
92%