Question

Consider the University database. 1\. Create a query to list all courses in a department (for which the user supplies the department code). 2\. Create a query to list all course titles where the user supplies both the department code and the credit hours. Note that two separate criteria, each with their own parameter, must be specified.

Short answer

The SQL queries would be: 'SELECT * FROM courses WHERE department_code = :department_code' for the first part of the exercise, and 'SELECT title FROM courses WHERE department_code = :department_code AND credit_hours = :credit_hours' for the second part.

Step-by-step solution

List all courses in a department

The objective in this first part of the exercise is to list all courses from a specific department, so an SQL 'SELECT' query would be appropriate. Assuming there is a table named 'courses' in the database, which has a column named 'department_code', the following query could be used: 'SELECT * FROM courses WHERE department_code = :department_code'. This query will return all rows from the 'courses' table where 'department_code' equals the value supplied by the user.

List all course titles for a specific department and credit hours

In this part, the task is to list all course titles based on two criteria: the department code and the credit hours. Therefore, a 'SELECT' query would be used again, with multiple conditions in the 'WHERE' clause. Suppose that, in addition to the 'department_code' column, there is also a 'credit_hours' column in the 'courses' table. The following query could be used: 'SELECT title FROM courses WHERE department_code = :department_code AND credit_hours = :credit_hours'. This query will return the 'title' from all rows in the 'courses' table where 'department_code' equals the value supplied by the user and 'credit_hours' also equals the provided value.

Key concepts

SELECT statement

The SELECT statement in SQL is fundamental for retrieving data from a database. It is used to select data from one or more tables: you specify the columns you want to retrieve, along with any conditions for filtering the results. For example, if you have a database with a table named courses, and you want to see every course offered by a department, you might write a query like SELECT * FROM courses, where * means 'all columns'. When looking for specific departments, you would add a condition with the WHERE clause, such as WHERE department_code = 'DEPT_CODE', where 'DEPT_CODE' represents the code of the department of interest.

By using the SELECT statement, students can obtain a list of all courses provided by a particular department. This is particularly useful in an educational database where departments offer various courses and students may wish to explore options within a certain field of study.

Department-based course listing

Department-based course listings are important for students who are focusing on a particular area of study. SQL queries allow for the easy retrieval of such lists from educational databases. Utilizing a department code, commonly stored in a column such as department_code, one can obtain a relevant course listing. For instance, to find all the courses in the Mathematics department, a query would be formatted as follows: SELECT * FROM courses WHERE department_code = 'MATH'.

Through this query, the database would return all records from the courses table where the department_code matches 'MATH'. If the requirement is more specific, say listing courses by both department and credit hours, this can also be achieved by expanding the WHERE clause to incorporate additional conditions, such as AND credit_hours = 3. This feature proves instrumental in aiding students to tailor their academic schedule according to department offerings and credit requirements.

Parameterized SQL queries

Parameterized SQL queries are a secure and flexible way to query a database. Rather than hard-coding the values into the SQL statement, you use placeholders that are later substituted with actual values supplied by the user. This not only prevents SQL injection attacks but also makes it simple to run the same query with different parameters. In the educational database example, a parameterized query to list courses by department could be written as: SELECT * FROM courses WHERE department_code = :department_code.

The placeholder :department_code is where the user-specified department code will be used when the query is executed. Similarly, to list course titles by department and credit hours, you might use SELECT title FROM courses WHERE department_code = :department_code AND credit_hours = :credit_hours, with :department_code and :credit_hours as parameters. When you execute a parameterized query, you provide the actual values – like 'CS' for Computer Science or '4' for four credit hours – which the database engine will use to retrieve the correct data. This technique enhances security and usability of SQL queries in an educational setting.