Consider the Student Relation: Student(StudentID, Name, Cohort, Gender).What does the following query return?

select count(StudentID) from Student where Cohort = 'C';

Question

Consider the Student Relation: Student(StudentID, Name, Cohort, Gender).What does the following query return?
 
select count(StudentID) from Student where Cohort = 'C';

BlackTom AI · Accepted Answer

We start by restating the scenario and the query to make sure the intent is clear.
Question: Consider the Student relation Student(StudentID, Name, Cohort, Gender). What does the following query return?
select count(StudentID) from Student where Cohort = 'C';

Now, evaluate each answer option in light of what the query does:

Option 1: The number of students in cohort 'C'.
This option matches the semantics of the query. The query counts the number of StudentID values for all rows where Cohort equals 'C'. Since StudentID identifies students, counting those IDs for the rows with Cohort 'C' yields the number of students in cohort C. The where clause restricts the rows to cohort C, and count(StudentID) tallies how many such rows exist.

Option 2: The number of cohorts.
This is incorrect because the query does not count distinct cohorts or any concept of cohorts. It operates on rows of the Student relation and uses count(StudentID), which counts rows (students) in the filtered set, not distinct cohort categories.

Option 3: The sum of student IDs in cohort 'C'.
This would require an aggregate like sum(StudentID). The query uses count(StudentID), which sums up the number of rows, not the numeric values of StudentID. Therefore, it does not produce a sum of IDs.

Option 4: The total number of rows in the table.
This would be true if there were no where clause, i.e., count(*) over the entire table. However, the where Cohort = 'C' clause restricts the rows to only those with Cohort equal to 'C'. Consequently, only rows meeting that condition are counted, not every row in the table.

Summarizing the reasoning: the query filters for Cohort = 'C' and then counts the resulting rows by applying count to StudentID, which yields the number of students in cohort C rather than any other quantity like total students, distinct cohorts, or a sum of IDs.

2025FallDYN-T-SCM593-87040-87041-88901 Comprehensive Exam- Requires Respondus LockDown Browser

Consider the Student Relation: Student(StudentID, Name, Cohort, Gender).What does the following query return? select count(StudentID) from Student where Cohort = 'C';

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