Explanation:
count_if(member_id IS NULL) counts rows for which the Boolean expression evaluates to true. count(member_id) excludes NULL values and therefore counts non-NULL values instead. count_null and null(member_id) are not valid solutions for this task.
Which command returns the number of NULL values in the member_id column?
A
SELECT count(member_id) FROM my_table;
B
SELECT count(member_id) - count_null(member_id) FROM my_table;
C
SELECT count_if(member_id IS NULL) FROM my_table;
D
SELECT null(member_id) FROM my_table;
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