SELECT
COUNT(gender) AS male_num,
AVG(gpa) AS avg_gpa
FROM user_profile
WHERE
gender = 'male'
count()、where、group by 的先后执行顺序:
先 where 过滤, 再group by 分组拆分生成临时表,最后 cout求和、 合并临时表
SELECT
COUNT(gender) AS male_num,
AVG(gpa) AS avg_gpa
FROM user_profile
WHERE
gender = 'male'
count()、where、group by 的先后执行顺序:
先 where 过滤, 再group by 分组拆分生成临时表,最后 cout求和、 合并临时表