SQL Exercise: List the number of employees in each department
SQL employee Database: Exercise-101 with Solution
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101. From the following table, write a SQL query to identify departments with fewer than four employees. 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)
Explanation:
The said query in SQL that retrieves the "dep_id" column and counts the number of rows in the 'employees' table for each unique "dep_id".
The HAVING clause include only those groups where the count of rows is less than 4.
Relational Algebra Expression:
Relational Algebra Tree:
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Sample Database: employee
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