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SQL Exercise: List the employees who are either CLERK or MANAGER

SQL employee Database: Exercise-40 with Solution

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40. From the following table, write a SQL query to find those employees who are either CLERK or MANAGER. Return complete information about the employees.

Sample table: employees


Pictorial Presentation:

SQL exercises on employee Database: List the employees who are either CLERK or MANAGER

Sample Solution:

SELECT *
FROM employees
WHERE job_name IN ('CLERK','MANAGER');

Sample Output:

 emp_id | emp_name | job_name | manager_id | hire_date  | salary  | commission | dep_id
--------+----------+----------+------------+------------+---------+------------+--------
  66928 | BLAZE    | MANAGER  |      68319 | 1991-05-01 | 2750.00 |            |   3001
  67832 | CLARE    | MANAGER  |      68319 | 1991-06-09 | 2550.00 |            |   1001
  65646 | JONAS    | MANAGER  |      68319 | 1991-04-02 | 2957.00 |            |   2001
  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
(7 rows)

Explanation:

The said query in SQL that retrieves all columns from the 'employees' table.

The WHERE clause includes rows that the "job_name" column must be equal to either 'CLERK' or 'MANAGER'.

Relational Algebra Expression:

Relational Algebra Expression: List the employees who are either CLERK or MANAGER.

Relational Algebra Tree:

Relational Algebra Tree: List the employees who are either CLERK or MANAGER.

Practice Online


Sample Database: employee

employee database structure

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Previous SQL Exercise: List ID, name, salary, and job_name of the employees.
Next SQL Exercise: All employees except those who joined in February.

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SQL: Tips of the Day

Grouped LIMIT in PostgreSQL: Show the first N rows for each group?

db=# SELECT * FROM xxx;
 id | section_id | name
----+------------+------
  1 |          1 | A
  2 |          1 | B
  3 |          1 | C
  4 |          1 | D
  5 |          2 | E
  6 |          2 | F
  7 |          3 | G
  8 |          2 | H
(8 rows)

I need the first 2 rows (ordered by name) for each section_id, i.e. a result similar to:

id | section_id | name
----+------------+------
  1 |          1 | A
  2 |          1 | B
  5 |          2 | E
  6 |          2 | F
  7 |          3 | G
(5 rows)

PostgreSQL v9.3 you can do a lateral join

select distinct t_outer.section_id, t_top.id, t_top.name from t t_outer
join lateral (
    select * from t t_inner
    where t_inner.section_id = t_outer.section_id
    order by t_inner.name
    limit 2
) t_top on true
order by t_outer.section_id;

Database: PostgreSQL

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

 





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