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.)
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SUM(start_date)
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AVG(start_date)
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COUNT(start_date)
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AVG(start_date, end_date)
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MIN(start_date)
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MAXIMUM(start_date)
COUNT works on any data type including dates - it counts non-null values. MIN and MAX can compare dates chronologically. SUM and AVG don't make sense on dates (can't add or average dates). MAXIMUM (F) is invalid - the correct function is MAX. Option D's AVG with two parameters is also invalid syntax.
To determine which two aggregate functions are valid on the START_DATE column, let's go through each option:
A. SUM(start_date) - This option is incorrect because the SUM function is used to calculate the sum of numeric values, not dates.
B. AVG(start_date) - This option is incorrect because the AVG function is used to calculate the average of numeric values, not dates.
C. COUNT(start_date) - This option is correct because the COUNT function can be used to count the number of occurrences of a column, including dates.
D. AVG(start_date, end_date) - This option is incorrect because the AVG function can only be used on a single column, not multiple columns.
E. MIN(start_date) - This option is correct because the MIN function can be used to find the minimum value in a column, including dates.
F. MAXIMUM(start_date) - This option is incorrect because there is no MAXIMUM function in SQL. The correct function is MAX, which can be used to find the maximum value in a column, including dates.
Therefore, the two valid aggregate functions on the START_DATE column are:
C. COUNT(start_date)
E. MIN(start_date)
The correct answer is C and E.