Counting Unique Subjects

Problem

The academic dean is reviewing the curriculum design and wants to know how many distinct subject areas are currently covered by the available courses. Count the number of unique subject values in the courses table.

Database Schema

Table: students

• id (INT): Unique identifier for the student.
• name (VARCHAR): Full name of the student.
• grade_level (INT): The student's current grade level (9-12).
• enrollment_year (INT): The year the student enrolled.

Table: courses

• id (INT): Unique identifier for the course.
• name (VARCHAR): Name of the course.
• subject (VARCHAR): Subject area (e.g., Math, Science).
• credits (INT): Number of course credits.

Table: grades

• id (INT): Unique identifier for the grade entry.
• student_id (INT): Foreign key referencing the student.
• course_id (INT): Foreign key referencing the course.
• score (INT): Numeric score (0-100).
• term (VARCHAR): Term of the grade (e.g., Fall 2022).

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Solution