SELECT student_id, section, sum(case when response=1 then 1 else 0 end) as total
FROM raw_data_r GROUP BY student_id, section
请注意,没有WHERE
条件。
mysql SELECT COUNT(*)'GROUP BY'不返回计数为零的行
SELECT student_id, section, sum(case when response=1 then 1 else 0 end) as total
FROM raw_data_r GROUP BY student_id, section
请注意,没有WHERE
条件。