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SQL exercises on employee Database: List all the employees whose designation is CLERK

SQL employee Database: Exercise-20 with Solution

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20. From the following table, write a SQL query to find those employees whose designation is ‘CLERK’. Return complete information about the employees.

Sample table: employees

Pictorial Presentation:

Sample Solution:

``````SELECT *
FROM employees
WHERE job_name = 'CLERK';
``````

Sample Output:

``` emp_id | emp_name | job_name | manager_id | hire_date  | salary  | commission | dep_id
--------+----------+----------+------------+------------+---------+------------+--------
63679 | SANDRINE | CLERK    |      69062 | 1990-12-18 |  900.00 |            |   2001
68736 | ADNRES   | CLERK    |      67858 | 1997-05-23 | 1200.00 |            |   2001
69000 | JULIUS   | CLERK    |      66928 | 1991-12-03 | 1050.00 |            |   3001
69324 | MARKER   | CLERK    |      67832 | 1992-01-23 | 1400.00 |            |   1001
(4 rows)
```

Relational Algebra Expression:

Relational Algebra Tree:

Practice Online

Sample Database: employee

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SQL: Tips of the Day

Delete all Duplicate Rows except for One in MySQL?

```SELECT * FROM names;

+----+--------+
| id | name   |
+----+--------+
| 1  | google |
| 2  | yahoo  |
| 3  | msn    |
| 4  | google |
| 5  | google |
| 6  | yahoo  |
+----+--------+
```

1. If you want to keep the row with the lowest id value:

```DELETE n1 FROM names n1, names n2 WHERE n1.id > n2.id AND n1.name = n2.name
```

2. If you want to keep the row with the highest id value:

```DELETE n1 FROM names n1, names n2 WHERE n1.id < n2.id AND n1.name = n2.name
```

Ref: https://bit.ly/3NroM8o