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SQL Exercise: Departments where more than two employees are working

SQL JOINS: Exercise-29 with Solution

From the following tables write a SQL query to find the names of departments where more than two employees are employed. Return dpt_name.

Sample table:emp_department


Sample table: emp_details


Sample Solution:

SELECT emp_department.dpt_name
  FROM emp_details 
     INNER JOIN emp_department
       ON emp_dept =dpt_code
        GROUP BY emp_department.dpt_name
          HAVING COUNT(*) > 2;

Output of the Query:

dpt_name
Finance
IT
HR

Explanation:

The said SQL query is selecting the 'dpt_name' column from the emp_department table.
This code is joining the emp_details table with the emp_department table on the matching value in the 'emp_dept' column of the emp_details table and the 'dpt_code' column of the emp_department table.
The query also use GROUP BY clause that groups the result-set by one or more columns.
The HAVING clause is used in conjunction with the GROUP BY clause. It is used to filter groups based on a specified condition, in this case, the condition is COUNT(*) > 2, which means it will only return the groups that have more than 2 rows.
It returns the name of the department whose count of employees is more than 2.

Relational Algebra Expression:

Relational Algebra Expression: Find the names of departments where more than two employees are working.

Relational Algebra Tree:

Relational Algebra Tree: Find the names of departments where more than two employees are working.

Practice Online


Query Visualization:

Duration:

Query visualization of Find the names of departments where more than two employees are working - Duration

Rows:

Query visualization of Find the names of departments where more than two employees are working - Rows

Cost:

Query visualization of Find the names of departments where more than two employees are working - Cost

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Previous SQL Exercise: Find employees and departments with a given budget.
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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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