从表中对特定学生的分数进行分组，并在每个学生的单独列中显示总分?
mysqlmysqli database
要对分数进行分组，请使用 MySQL GROUP BY。要求和，请使用 MySQL sum() 函数。让我们首先创建一个表 −
mysql> create table DemoTable1920 ( StudentName varchar(20), StudentMarks int ); Query OK, 0 rows affected (0.00 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable1920 values('Chris',67);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1920 values('David',97);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1920 values('Chris',57);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1920 values('David',45);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1920 values('Chris',89);
Query OK, 1 row affected (0.00 sec)
使用 select 语句显示表中的所有记录 −
mysql> select * from DemoTable1920;
这将产生以下输出 −
+-------------+--------------+ | StudentName | StudentMarks | +-------------+--------------+ | Chris | 67 | | David | 97 | | Chris | 57 | | David | 45 | | Chris | 89 | +-------------+--------------+ 5 rows in set (0.00 sec)
以下是对特定学生的成绩进行分组的查询 −
mysql> select StudentName,SUM(StudentMarks) as TotalMarks from DemoTable1920 group by StudentName;
这将产生以下输出 −
+-------------+------------+ | StudentName | TotalMarks | +-------------+------------+ | Chris | 213 | | David | 142 | +-------------+------------+ 2 rows in set (0.00 sec)
