在 MySQL 中根据表值添加整数的有效方法是什么?
mysqlmysqli database
您需要使用 GROUP BY 子句。让我们首先创建一个 −
mysql> create table DemoTable1443 -> ( -> StudentId int, -> StudentScore int -> ); Query OK, 0 rows affected (0.42 sec)
使用 insert 在表中插入一些记录 −
mysql> insert into DemoTable1443 values(100,78); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable1443 values(101,89); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1443 values(100,88); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1443 values(101,97); Query OK, 1 row affected (0.12 sec)
使用 select 语句显示表中的所有记录 −
mysql> select * from DemoTable1443;
这将产生以下输出 −
+-----------+--------------+ | StudentId | StudentScore | +-----------+--------------+ | 100 | 78 | | 101 | 89 | | 100 | 88 | | 101 | 97 | +-----------+--------------+ 4 rows in set (0.00 sec)
以下是根据表值添加整数的查询 −
mysql> select StudentId,sum(StudentScore) from DemoTable1443 -> group by StudentId;
这将产生以下输出 −
+-----------+-------------------+ | StudentId | sum(StudentScore) | +-----------+-------------------+ | 100 | 166 | | 101 | 186 | +-----------+-------------------+ 2 rows in set (0.00 sec)
