PostgreSQL JOINS: Make a join with table employees and itself to find the employee id, name, manager_id and manager name
4. Write a query to make a join with two tables employees and itself to find the employee id, last_name as Employee along with their manager_id and last name as Manager.
Sample Solution:
Code:
SELECT W1.employee_id as "Emp_id" , W1.last_name AS "Employee",
W2.employee_id AS "Manager ID", W2.last_name AS "Manager"
FROM employees W1 JOIN employees W2
ON W1.manager_id= W2.employee_id;
Sample table: employees
Output:
pg_exercises=# SELECT W1.employee_id as "Emp_id" , W1.last_name AS "Employee", pg_exercises-# W2.employee_id AS "Manager ID", W2.last_name AS "Manager" pg_exercises-# FROM employees W1 JOIN employees W2 pg_exercises-# ON W1.manager_id= W2.employee_id; Emp_id | Employee | Manager ID | Manager --------+-------------+------------+----------- 103 | Hunold | 102 | De Haan 104 | Ernst | 103 | Hunold 105 | Austin | 103 | Hunold 106 | Pataballa | 103 | Hunold 107 | Lorentz | 103 | Hunold 114 | Raphaely | 100 | King 115 | Khoo | 114 | Raphaely 116 | Baida | 114 | Raphaely 117 | Tobias | 114 | Raphaely 101 | Kochhar | 100 | King 118 | Himuro | 114 | Raphaely 119 | Colmenares | 114 | Raphaely 133 | Mallin | 122 | Kaufling 134 | Rogers | 122 | Kaufling 135 | Gee | 122 | Kaufling 136 | Philtanker | 122 | Kaufling 138 | Stiles | 123 | Vollman 139 | Seo | 123 | Vollman 140 | Patel | 123 | Vollman 141 | Rajs | 124 | Mourgos 142 | Davies | 124 | Mourgos ... 203 | Mavris | 101 | Kochhar 204 | Baer | 101 | Kochhar 205 | Higgins | 101 | Kochhar 206 | Gietz | 205 | Higgins (105 rows)
Practice Online
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Previous: Write a SQL query to make a join with three tables employees, departments and locations to find the name, including first_name and last_name, jobs, department name and ID, of the employees working in London.
Next: Write a query to make a join with a table employees and itself to find the name, including first_name and last_name and hire date for those employees who were hired after the employee Jones.
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