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SQL exercises on employee Database: List the no. of employees in each department where the no. is less than 4

SQL employee Database: Exercise-101 with Solution

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101. From the following tables, write a SQL query to find those departments where less than four employees work. Return department ID, number of employees.

Sample table: employees


Sample Solution:

SELECT dep_id,
       count(*)
FROM employees
GROUP BY dep_id
HAVING count(*)<4;

Sample Output:

 dep_id | count
--------+-------
   1001 |     3
(1 row)

Relational Algebra Expression:

Relational Algebra Expression: List the no. of employees in each department where the no. is less than 4.

Relational Algebra Tree:

Relational Algebra Tree: List the no. of employees in each department where the no. is less than 4.

Practice Online


Sample Database: employee

employee database structure

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Previous: From the following table, write a SQL query to find those departments where at least two employees work as a SALESMAN in each grade. Return department name, grade and number of employees.
Next: From the following tables, write a SQL query to find those departments where at least two employees work. Return department name, number of employees.

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