Question

Consider the University database: 1\. For each department list the department code and the largest value for credit hours. 2\. For each department list the department code, department name, and the number of courses.

Short answer

In order to solve the exercise, two different queries must be executed. The first query using the MAX function to find the department with the maximum credit hours, and the second one using the COUNT function to determine the number of courses in each department.

Step-by-step solution

Understanding problem and Preparing for Solution

Here we are dealing with a relational database where there's probably a Department and a Course table and are somehow related. We assume that the Department table has columns including department_code and department_name. The Course table likely includes columns such as department_code and credit_hours, among others. With this understanding, we can begin solving the exercise

- Query for Maximum Credit Hours

To find the department_code along with the highest value for credit_hours among the courses offered by each department, we can use the MAX() aggregate function in the query. It would look like this: SELECT department_code, MAX(credit_hours) AS max_credit_hours FROM Course GROUP BY department_code ;

- Query for Number of Courses

For finding the department_code, department_name, and the number of courses offered by each department, we must use the COUNT() function. Here, we can use INNER JOIN to fetch data from multiple tables. The query would look like this: SELECT d.department_code, d.department_name, COUNT(c.course_id) AS num_coursesFROM Department d INNER JOIN Course c ON d.department_code = c.department_code GROUP BY d.department_code, d.department_name ;

Key concepts

Relational Databases

A relational database is a type of database that organizes data into tables, which can be related to each other through common fields. These tables consist of rows and columns, where each row represents a unique record, and each column represents a field within the record. Relational databases are particularly powerful because they allow complex queries and operations on the data without redundancy.
For example, a university database might include a "Department" table and a "Course" table. Each table would have columns for storing different pieces of information, such as department names and course details. These tables can be linked through a common identifier, such as the department code. This relational model ensures that data remains organized, accurate, and easy to retrieve.

• Tables: Organize data into rows and columns.
• Relationships: Define connections between different tables using keys.
• Normal forms: Standards that ensure database efficiency and eliminate data redundancy.

MAX Function

The MAX function in SQL is used to find the largest value in a set of values. It is an aggregate function, meaning it processes multiple rows and returns a single result based on those rows. This can be particularly useful when you need to determine the maximum value of a column, such as finding the highest credit hours for courses within each department.
In the context of the university database, suppose you want to find out the maximum credit hours for courses in each department. You can do that with the following query:
SELECT department_code, MAX(credit_hours) AS max_credit_hours FROM Course GROUP BY department_code;
This query groups courses by department and finds the maximum credit hours for each group, giving you a snapshot of the most demanding courses each department offers.

COUNT Function

The COUNT function in SQL is another aggregate function, with the main purpose of returning the total number of rows that match a specific condition or criteria. When you want to find how many records exist in a table or how many specific items satisfy a certain condition, COUNT will be your go-to function.
For instance, if you want to determine how many courses are offered by each department in the university database, you can use the COUNT function to achieve this. Here’s how it looks:
SELECT d.department_code, d.department_name, COUNT(c.course_id) AS num_courses FROM Department d INNER JOIN Course c ON d.department_code = c.department_code GROUP BY d.department_code, d.department_name;
This query effectively counts the number of courses associated with each department by joining the "Department" table with the "Course" table and grouping the results by departments.

INNER JOIN

The INNER JOIN operation in SQL is a powerful tool for combining rows from two or more tables based on a related column between them. When you use an INNER JOIN, the result will only include rows where there is a match in both tables for a specified condition.
This is particularly useful in relational databases where data is normalized across multiple tables. For example, in the university database scenario, information about departments and their courses resides in separate tables. To get a complete picture like the number of courses each department offers, you need to join these tables using the INNER JOIN.
Here's an example query that demonstrates this:

• SELECT d.department_code, d.department_name, COUNT(c.course_id) AS num_courses
• FROM Department d INNER JOIN Course c ON d.department_code = c.department_code
• GROUP BY d.department_code, d.department_name;

This query essentially combines the "Department" and "Course" tables by matching department codes, providing a comprehensive list of departments along with the count of courses offered.