如何使用 ORDER BY 在 MySQL 中对同名学生的分数进行求和?
mysqlmysqli database更新于 2025/5/24 13:00:17
为此，请使用 ORDER BY 和 GROUP BY 子句。让我们首先创建一个包含学生姓名和分数的表 −
mysql> create table countRowValueDemo -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(20), -> StudentMathScore int -> ); Query OK, 0 rows affected (0.71 sec)
下面是使用 insert 命令向表中插入记录的查询 −
mysql> insert into countRowValueDemo(StudentName,StudentMathScore) values('Larry',45);
Query OK, 1 row affected (0.19 sec)
mysql> insert into countRowValueDemo(StudentName,StudentMathScore) values('Mike',56);
Query OK, 1 row affected (0.16 sec)
mysql> insert into countRowValueDemo(StudentName,StudentMathScore) values('John',60);
Query OK, 1 row affected (0.15 sec)
mysql> insert into countRowValueDemo(StudentName,StudentMathScore) values('David',40);
Query OK, 1 row affected (0.24 sec)
mysql> insert into countRowValueDemo(StudentName,StudentMathScore) values('David',70);
Query OK, 1 row affected (0.12 sec)
mysql> insert into countRowValueDemo(StudentName,StudentMathScore) values('John',80);
Query OK, 1 row affected (0.13 sec)
mysql> insert into countRowValueDemo(StudentName,StudentMathScore) values('David',88);
Query OK, 1 row affected (0.17 sec)
以下是使用 select 语句显示表中的所有记录的查询 −
mysql> select * from countRowValueDemo;
这将产生以下输出 −
+-----------+-------------+------------------+ | StudentId | StudentName | StudentMathScore | +-----------+-------------+------------------+ | 1 | Larry | 45 | | 2 | Mike | 56 | | 3 | John | 60 | | 4 | David | 40 | | 5 | David | 70 | | 6 | John | 80 | | 7 | David | 88 | +-----------+-------------+------------------+ 7 rows in set (0.00 sec)
案例 1:降序(求和)
以下查询用于对姓名相似的学生的分数求和。结果将按降序显示 −
mysql> select StudentName, -> sum(StudentMathScore) AS TOTAL_SCORE -> from countRowValueDemo -> group by StudentName -> order by sum(StudentMathScore) desc;
这将产生以下输出 −
+-------------+-------------+ | StudentName | TOTAL_SCORE | +-------------+-------------+ | David | 198 | | John | 140 | | Mike | 56 | | Larry | 45 | +-------------+-------------+ 4 rows in set (0.00 sec)
案例 2: 升序(求和)
以下查询用于对姓名相似的学生的分数求和。结果将按降序显示 −
mysql> select StudentName, -> sum(StudentMathScore) AS TOTAL_SCORE -> from countRowValueDemo -> group by StudentName -> order by sum(StudentMathScore);
这将产生以下输出 −
+-------------+-------------+ | StudentName | TOTAL_SCORE | +-------------+-------------+ | Larry | 45 | | Mike | 56 | | John | 140 | | David | 198 | +-------------+-------------+ 4 rows in set (0.00 sec)
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