Question

Consider the University database. 1\. Create a query to list the department codes (with no duplicates) of departments that offer 6 credit hour courses. 2\. Modify your query to list the department names too.

Short answer

1. The SQL query to get department codes of departments offering 6 credit hour courses is: SELECT DISTINCT dept_code FROM Courses WHERE credit_hours = 6; 2. The modified query to get department names as well is: SELECT DISTINCT dept_code, dept_name FROM Courses WHERE credit_hours = 6;

Step-by-step solution

Write the SQL query to list distinct department codes offering 6 credit hours

The keyword DISTINCT is used to return unique results in the query results. The WHERE clause is used to filter the results by selecting departments offering courses of 6 credit hours. The query should be written like: \n\n SELECT DISTINCT dept_code FROM Courses WHERE credit_hours = 6;

Test Your Query

Run your query in your SQL environment to see if it returns the expected results. Make sure that no duplicate department codes are returned in the results and only the departments offering 6 credit hour courses are listed.

Modify the Query to include Department Names

To add department names to the result, just extend the SELECT statement with the dept_name attribute. The modified query should be written like: \n\n SELECT DISTINCT dept_code, dept_name FROM Courses WHERE credit_hours = 6;

Test Your Modified Query

Rerun your modified query in your SQL environment. This time it should return not only the distinct department codes but also the department names of those departments that offer 6 credit hour courses.

Key concepts

University Database

A University Database is designed to store and manage data related to a university's operations and entities. This includes information about students, courses, departments, faculty, and staff. Think of it as a well-organized digital filing cabinet that contains all the information needed for administrative and academic purposes. In this context, we're focusing on the departments and their associated courses.
University databases typically involve multiple tables representing different data entities, such as 'Students', 'Courses', and 'Departments'. These tables are usually interrelated, allowing users to extract specific information via SQL queries.

• Tables: Organized collections of data, each representing a single entity.
• Queries: Requests to retrieve specific information from the database.
• Relationships: Connections between tables that define how data types interrelate.

Being able to query a university database effectively is crucial for managing data like course offers, faculty assignments, and student enrollments.

DISTINCT Keyword

In SQL, the DISTINCT keyword is used to ensure the results only include unique entries. This is particularly useful when a column might have duplicate values. For instance, different courses might belong to the same department, which means the department code could appear more than once in your query results.
Using DISTINCT can help us refine our results to avoid repetition and improve readability. When querying a database for unique department codes offering 6 credit hour courses, adding DISTINCT filters out duplicate instances.
Here's a simple explanation of its role:

• Filter: Eliminates duplicates from your query results.
• Simplifies: Makes lists more readable and concise.
• Specificity: Returns a unique set of results based on the column specified.

Using DISTINCT ensures the output from your SQL queries is clean and precise, highlighting only the necessary information.

SQL SELECT Statement

The SQL SELECT statement is fundamental when working with databases as it allows you to retrieve data from one or more tables. It is the equivalent of asking a question of the database to get specific information.
In our context, we use SELECT to obtain department codes and names offering 6 credit hour courses. The syntax we use looks something like this: \(\text{SELECT DISTINCT dept_code, dept_name FROM Courses WHERE credit_hours = 6;} \)
This statement does a few things:

• Columns: Identifies which columns' data are needed – here, ‘dept_code’ and ‘dept_name’.
• Filtering: Focuses the results on entries where specific conditions are true, set by a WHERE clause.

The SELECT statement is powerful because it can gather and display the exact dataset required, all based on user-defined criteria. It forms the backbone of most data retrieval tasks in database management.

SQL WHERE Clause

The SQL WHERE clause is a powerful tool used to filter records and extract only those that meet specified conditions from a table. It acts as a filter, refining the results of your query to be more precise.
For the task at hand, the WHERE clause is crucial in narrowing down the departments to those that offer exactly 6 credit hour courses. Here's how it works:

• Condition Specific: Retrieves rows that fulfill the stated conditions.
• Flexibility: Can handle multiple conditions using logical operators like AND, OR, and NOT.

For example: \(\text{WHERE credit_hours = 6;}\)
This part of the SQL statement ensures that only rows with courses of exactly 6 credit hours are selected, making your query highly efficient at targeting specific data subsets.