SQL Exercise: List all the employees who report to Blaze
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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
+-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+ | EMPLOYEE_ID | FIRST_NAME | LAST_NAME | EMAIL | PHONE_NUMBER | HIRE_DATE | JOB_ID | SALARY | COMMISSION_PCT | MANAGER_ID | DEPARTMENT_ID | +-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+ | 100 | Steven | King | SKING | 515.123.4567 | 2003-06-17 | AD_PRES | 24000.00 | 0.00 | 0 | 90 | | 101 | Neena | Kochhar | NKOCHHAR | 515.123.4568 | 2005-09-21 | AD_VP | 17000.00 | 0.00 | 100 | 90 | | 102 | Lex | De Haan | LDEHAAN | 515.123.4569 | 2001-01-13 | AD_VP | 17000.00 | 0.00 | 100 | 90 | | 103 | Alexander | Hunold | AHUNOLD | 590.423.4567 | 2006-01-03 | IT_PROG | 9000.00 | 0.00 | 102 | 60 | | 104 | Bruce | Ernst | BERNST | 590.423.4568 | 2007-05-21 | IT_PROG | 6000.00 | 0.00 | 103 | 60 | | 105 | David | Austin | DAUSTIN | 590.423.4569 | 2005-06-25 | IT_PROG | 4800.00 | 0.00 | 103 | 60 | | 106 | Valli | Pataballa | VPATABAL | 590.423.4560 | 2006-02-05 | IT_PROG | 4800.00 | 0.00 | 103 | 60 | | 107 | Diana | Lorentz | DLORENTZ | 590.423.5567 | 2007-02-07 | IT_PROG | 4200.00 | 0.00 | 103 | 60 | | 108 | Nancy | Greenberg | NGREENBE | 515.124.4569 | 2002-08-17 | FI_MGR | 12008.00 | 0.00 | 101 | 100 | | 109 | Daniel | Faviet | DFAVIET | 515.124.4169 | 2002-08-16 | FI_ACCOUNT | 9000.00 | 0.00 | 108 | 100 | ......... | 206 | William | Gietz | WGIETZ | 515.123.8181 | 2002-06-07 | AC_ACCOUNT | 8300.00 | 0.00 | 205 | 110 | +-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+
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.
Go to:
PREV : List all employees who are subordinates to Blaze.
NEXT : Names of the employees and the manager of JONAS.
Practice Online
Sample Database: employees
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