Multiple choice softskills teamwork

Examine the description of the STUDENTS table: STD_ID NUMBER(4) COURSE_ID VARCHAR2(10) START_DATE DATE END_DATE DATE Which two aggregate functions are valid on the START_DATE column? (Choose two.)

  1. SUM(start_date)

  2. AVG(start_date)

  3. COUNT(start_date)

  4. AVG(start_date, end_date)

  5. MIN(start_date)

  6. MAXIMUM(start_date)
Reveal answer Fill a bubble to check yourself
C,E Correct answer
Explanation

For DATE columns in Oracle, only COUNT, MIN, and MAX are valid aggregate functions because they work with ordered data and counting. SUM and AVG require numeric values to calculate totals and averages, which cannot be performed on dates. MAXIMUM (option F) is incorrect Oracle syntax - it must be MAX.

AI explanation

To answer this question, let's go through each option to determine which aggregate functions are valid on the START_DATE column:

Option A) SUM(start_date) - The SUM function is used to calculate the sum of numerical values. However, the START_DATE column is of type DATE, not a numerical value. Therefore, this option is incorrect.

Option B) AVG(start_date) - The AVG function is used to calculate the average of numerical values. Since the START_DATE column is of type DATE, this option is incorrect.

Option C) COUNT(start_date) - The COUNT function is used to count the number of rows or non-null values in a column. This function is valid for the START_DATE column since it counts the number of occurrences of the column values. Therefore, this option is correct.

Option D) AVG(start_date, end_date) - The AVG function calculates the average of numerical values. However, in this option, there are two columns provided (START_DATE and END_DATE), which is not valid for the AVG function. Therefore, this option is incorrect.

Option E) MIN(start_date) - The MIN function is used to find the minimum value in a column. Since the START_DATE column is of type DATE, this option is valid.

Option F) MAXIMUM(start_date) - The MAXIMUM function is not a valid aggregate function in SQL. Therefore, this option is incorrect.

The correct answers are C) COUNT(start_date) and E) MIN(start_date) because both functions are valid for the START_DATE column.

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