SQL COUNT DISTINCT 函数 定义和用法 语法 例子 "Orders"表： 例子 1 例子 2 SQL COUNT DISTINCT 函数 定义和用法 可以一同使用 DISTINCT 和 COUNT 关键词，来计算非重复结果的数目。 语法 SELECT COUNT ( DISTINCT column ( s )) ...

限制查询返回的记录数 限制查询返回的记录数 import mysql . connector   mydb = mysql . connector . connect ( host = "localhost" , user = "myusername" , passwd = "mypassword" , databa...

删除已有的表 删除已有的表 import mysql . connector   mydb = mysql . connector . connect ( host = "localhost" , user = "myusername" , passwd = "mypassword" , database = "my...

使用 fetchone()方法读取表中的单行 使用 fetchone()方法读取表中的单行 import mysql . connector   mydb = mysql . connector . connect ( host = "localhost" , user = "myusername" , passwd = ...

更新表中的已有记录 更新表中的已有记录 import mysql . connector   mydb = mysql . connector . connect ( host = "localhost" , user = "myusername" , passwd = "mypassword" , database...

获取所插入的 ID 获取所插入的 ID import mysql . connector   mydb = mysql . connector . connect ( host = "localhost" , user = "myusername" , passwd = "mypassword" , database...

从已有表中删除记录 从已有表中删除记录 import mysql . connector   mydb = mysql . connector . connect ( host = "localhost" , user = "myusername" , passwd = "mypassword" , database...

创建表 创建表 import mysql . connector   mydb = mysql . connector . connect ( host = "localhost" , user = "myusername" , passwd = "mypassword" , database = "mydataba...

防止 SQL 注入 防止 SQL 注入 import mysql . connector   mydb = mysql . connector . connect ( host = "localhost" , user = "myusername" , passwd = "mypassword" , database...

SQL DELETE 语句 DELETE 语句 语法 Person: 删除某行 结果: 删除所有行 SQL DELETE 语句 DELETE 语句 DELETE 语句用于删除表中的行。 语法 DELETE FROM 表名称 WHERE 列名称 = 值 Person: LastName Fi...