SQL Exercise: Find employees who works either in department 70 or 90

Last update on March 31 2023 06:07:12 (UTC/GMT +8 hours)

SQL SORTING and FILTERING on HR Database: Exercise-13 with Solution

13. From the following table, write a SQL query to find those employees who work either in department 70 or 90. Return full name (first and last name), department id.

Sample table : employees

Sample Solution:

SELECT first_name ||' '|| last_name AS Full_Name, department_id
  FROM employees
   WHERE department_id = 70 
     OR department_id = 90;

SELECT first_name ||' '|| last_name AS Full_Name, department_id
 FROM employees
  WHERE department_id IN (70 , 90);

Sample Output:

   full_name   | department_id
---------------+---------------
 Steven King   |            90
 Neena Kochhar |            90
 Lex De Haan   |            90
 Hermann Baer  |            70
(4 rows)

Code Explanation:

The said query in SQL that retrieves the first name and last name concatenated as "Full_Name" and the "department_id" from the 'employees' table where the "department_id" is either 70 or 90.

Practice Online

Query Visualization for Sample Solution:

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Query Visualization for alternate Sample Solution:

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Previous SQL Exercise: Employees who was hired during given dates.
Next SQL Exercise: Find those employees who is working under a manager.

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SQL: Tips of the Day

Difference between natural join and inner join

One significant difference between INNER JOIN and NATURAL JOIN is the number of columns returned-

Consider:

TableA                           TableB
+------------+----------+        +--------------------+    
|Column1     | Column2  |        |Column1  |  Column3 |
+-----------------------+        +--------------------+
| 1          |  2       |        | 1       |   3      |
+------------+----------+        +---------+----------+

The INNER JOIN of TableA and TableB on Column1 will return

SELECT * FROM TableA AS a INNER JOIN TableB AS b USING (Column1);
SELECT * FROM TableA AS a INNER JOIN TableB AS b ON a.Column1 = b.Column1;

+------------+-----------+---------------------+    
| a.Column1  | a.Column2 | b.Column1| b.Column3|
+------------------------+---------------------+
| 1          |  2        | 1        |   3      |
+------------+-----------+----------+----------+

The NATURAL JOIN of TableA and TableB on Column1 will return:

SELECT * FROM TableA NATURAL JOIN TableB
+------------+----------+----------+    
|Column1     | Column2  | Column3  |
+-----------------------+----------+
| 1          |  2       |   3      |
+------------+----------+----------+

Ref: https://bit.ly/3AG5CId

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