How to Display Zero Counts for Employees Without Subscriptions in SQL Queries?

Addressing SQL Query Issue: Displaying Zero Counts in COUNT Aggregation

In the scenario presented, the objective is to determine the subscription count for all employees, even those without entries in the mailing subscriptions table. The initial query using an inner join only returned counts for employees with matching records in the mailing subscriptions table, excluding employees without subscriptions.

To resolve this, consider using a left join (LEFT JOIN) in the query. A left join preserves all rows from the left table (Employee), even if there are no matching rows in the right table (mailingSubscriptions). The following query incorporates a left join to achieve the desired result:

SELECT c.name, count(m.mailid)
FROM Employee c
LEFT JOIN mailingSubscriptions m ON c.Name = m.EmployeeName
GROUP BY c.name;

This revised query ensures that all employees are included in the results, and the COUNT aggregation will return 0 for employees without matching subscriptions in the mailingSubscriptions table. The outer join eliminates the limitation of inner joins, which only display rows with matching records in both tables.

By executing the modified query with a left join, the table will correctly display subscription counts for all employees, including those without subscriptions. This provides a complete and accurate representation of the data, considering both employees with and without subscriptions in the mailingSubscriptions table.

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