Which of the following commands will return the number of null values in the member_id column?

Question

Options

• ASELECT count(member_id) FROM my_table;
• BSELECT count(member_id) - count_null(member_id) FROM my_table;
• CSELECT count_if(member_id IS NULL) FROM my_table;
• DSELECT null(member_id) FROM my_table;
• ESELECT count_null(member_id) FROM my_table;

• A
  7% (2)
• B
  4% (1)
• C
  85% (23)
• E
  4% (1)

Explanation

count_if(condition) is a SQL aggregate function that counts the number of rows where the specified boolean condition evaluates to true. Using count_if(member_id IS NULL) directly counts rows where member_id is NULL, which is exactly the goal. Option A - count(member_id) - is a common trap: SQL's count() function ignores NULL values by design, so it returns the count of non-null rows, not null rows. count_null() and null() are not valid standard SQL functions. Option B mixes valid and invalid functions.

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