题解 | countif用法
计算男生人数以及平均GPA
http://www.nowcoder.com/practice/7d9a7b2d6b4241dbb5e5066d7549ca01
select COUNT(if(t.gender ='male', true,1)), round(avg(t.gpa),1) from # 到小数点后一位 (select gender,gpa from user_profile where gender = 'male') tcount(if(xx,true,1)) 写法要记住