COUNTとSUM
2327 ワード
COUNT ,COUNT(*) ,COUNT(1) ,1 。
count() , 。
Sum() , , 。
NULL ,COUNT( ) SUM( ) 。
Count Null , expr (*) dadefWildcardCharacters. ,Count , Null 。Count(*) Count ([Column Name]) 。 SUM( ), 1; COUNT( ), , NULL 1; select student_id,sum(score) as sum_all_score, sum(score > 60) as sum_score_passed, count(score) as count_all_score, count(score > 60) as count_score_passed, avg(score) as avg_score from tbl_score group by student_id having sum(score>60) >=2;