分组统计(group by)时 条件统计某列值的行数

写道

//分组统计时 条件统计某列值的行数
String sql = "select UserId,count(case TrueFalse when true then UserId end) as rightAnswer,"+
"count(case TrueFalse when false then UserId end) as errorAnswer "+
from evastatistics GROUP BY UserId";