Multiple choice technology databases

Examine the description of the STUDENTS table: STD_ID NUMBER(4) COURSE_ID VARCHARD2(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. COUNT(start_date)

  3. AVG(start_date, end_date)

  4. MIN(start_date)
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation

COUNT() and MIN() are valid aggregate functions on DATE columns - COUNT returns non-null count, MIN returns earliest date. SUM() requires numeric data. AVG() on two dates is invalid syntax. Only two options are correct.

AI explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) SUM(start_date) - This option is incorrect because the SUM function is used to calculate the sum of numeric values. The START_DATE column is of the DATE data type, which is not a numeric data type.

Option B) COUNT(start_date) - This option is correct. The COUNT function is used to count the number of rows in a column. It can be used on any data type, including the DATE data type.

Option C) AVG(start_date, end_date) - This option is incorrect because the AVG function is used to calculate the average of numeric values. It cannot be used with multiple columns.

Option D) MIN(start_date) - This option is correct. The MIN function is used to find the minimum value in a column. It can be used on the DATE data type.

Therefore, the two valid aggregate functions on the START_DATE column are COUNT(start_date) and MIN(start_date).

The correct answer is B,D.

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