﻿ SQL: Display Employees whose last name is McEwen

# SQL Exercise: Display Employees whose last name is McEwen

## SQL SORTING and FILTERING on HR Database: Exercise-3 with Solution

3. From the following table, write a SQL query to find those employees whose last name is "McEwen". Return first name, last name and department ID.

Sample table: employees

Sample Solution:

``````SELECT first_name, last_name, department_id
FROM employees
WHERE last_name = 'McEwen';
``````

Sample Output:

``` first_name | last_name | department_id
------------+-----------+---------------
Allan      | McEwen    |            80
(1 row)
```

Code Explanation:

The said query in SQL that retrieves first name, last name, and department ID columns from the "employees" table where the last name is 'McEwen'. As a result of the query, all the rows that meet the condition stipulated in the "WHERE" clause will be returned from the 'employees' table.

Relational Algebra Expression:

Relational Algebra Tree:

## Query Visualization:

Duration:

Rows:

Cost:

Previous SQL Exercise: Find those employees who earn more than 8000.
Next SQL Exercise: Details of employees without any department number.

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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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