SQL Exercise: Information about the department Marketing

Last update on March 31 2023 06:07:57 (UTC/GMT +8 hours)

SQL SORTING and FILTERING on HR Database: Exercise-5 with Solution

5. From the following table, write a SQL query to find the details of 'Marketing' department. Return all fields.

Sample table: departments

Sample Solution:

SELECT *
 FROM  departments
  WHERE department_name = 'Marketing';

Sample Output:

 department_id | department_name | manager_id | location_id
---------------+-----------------+------------+-------------
            20 | Marketing       |        201 |        1800
(1 row)

Code Explanation:

The said query in SQL that retrieves all columns from the 'departments' table where the department name is 'Marketing'. As a result of the query, a list of all rows in the 'departments' table that match the conditions specified in the "WHERE" clause is returned. The "SELECT *" clause retrieves all columns from the table.

Relational Algebra Expression:

Relational Algebra Tree:

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Query Visualization:

Duration:

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Previous SQL Exercise: Details of employees without any department number.
Next SQL Exercise: Employees first name does not contain the letter M .

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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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