SQL Exercise: List all the employees who report to Blaze

Last update on January 16 2025 07:16:06 (UTC/GMT +8 hours)

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48. From the following table, write a SQL query to find those employees who work as managers. Return complete information about the employees. Use co-related subquery.

Sample table: employees

Sample Solution:

SELECT *  -- Select all columns from the employees table (alias e1)
FROM employees e1  
WHERE emp_id IN (  
-- Subquery: Select the manager_id from the employees table (alias e2)
    SELECT manager_id  
    FROM employees e2  
-- Correlation: Match the department_id of e2 with the department_id of the current row in e1
    WHERE e2.dep_id = e1.dep_id  
); 

Sample Output:

 emp_id | emp_name | job_name  | manager_id | hire_date  | salary  | commission | dep_id
--------+----------+-----------+------------+------------+---------+------------+--------
  68319 | KAYLING  | PRESIDENT |            | 1991-11-18 | 6000.00 |            |   1001
  66928 | BLAZE    | MANAGER   |      68319 | 1991-05-01 | 2750.00 |            |   3001
  67832 | CLARE    | MANAGER   |      68319 | 1991-06-09 | 2550.00 |            |   1001
  65646 | JONAS    | MANAGER   |      68319 | 1991-04-02 | 2957.00 |            |   2001
  67858 | SCARLET  | ANALYST   |      65646 | 1997-04-19 | 3100.00 |            |   2001
  69062 | FRANK    | ANALYST   |      65646 | 1991-12-03 | 3100.00 |            |   2001
(6 rows)

Explanation:

• Outer Query (e1): Selects all columns from the employees table.
• Inner Query (e2): Retrieves manager_id from the employees table where the department_id matches the department_id of the current row in the outer query (e1).
• The inner query is co-related because it depends on the department_id of the outer query's current row.

This co-relation ensures the inner query dynamically adapts to each row of the outer query.

Practice Online

Structure of employee Database:

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Previous SQL Exercise: List all employees who are subordinates to Blaze.
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