Final Answer:
To elaborate, you fundamentally combine rows from two distinct tables based on a related column that exists in both tables. The statement is true, so the correct option is a.
Step-by-step explanation:
Assuming there are two tables, one named "department" and the other "employee", and they are related by a column such as "department_id" in the "employee" table that references an "id" column in the "department" table, we can perform a join operation to consolidate data from both tables.
Here is an outline of how one would go about solving this:
1. Identify the related column: Check both tables for a common column that will function as the link between them. In this case, the "department_id" column in the "employee" table would likely correspond to the "id" column in the "department" table.
2. Use a JOIN operation: Apply an SQL JOIN to merge the tables. A JOIN clause tells the database how to use the related columns to combine the rows.
The standard JOIN (commonly an INNER JOIN) will combine rows from both tables where the condition matches.
3. Aggregate the data: To find out how many employees work in each department, a COUNT function is utilized to count the number of rows (employees) that exist for each department after the join.
4. Group the results: The results are then grouped by the "department.name" using the GROUP BY clause so that the count of employees is organized by each distinct department.
The resulting SQL query would look something like this:
```sql
SELECT department.name, COUNT(employee.id)
FROM employee
JOIN department ON employee department_id = department.id
GROUP BY department.name
```
This query would return a set of records where each record contains a department name and the corresponding number of employees that work in that department.
Please note that this process assumes that there is a relational database system in place, with the two tables properly defined and populated with data.
The count will only include the departments that have at least one employee due to the nature of an INNER JOIN.
If you wanted to include departments with zero employees, you would use a LEFT JOIN instead, which would ensure all departments are listed, including those without associated employees.
So the correct option is a.