SELECT , t2.salary FROM employee AS t1 INNER JOIN info AS t2 ON = ; 可以对数据表使用别名3. ,运算符例如SELECT * FROM table1,table2 由于在MySQL中INNER JOIN与CROSS JOIN相同,INNER JOIN和 , 在MySQL也相同,都是产生两个表的笛卡尔积Cartesian Prod
步骤3: 执行 INNER JOIN 查询 现在,我们可以使用 INNER JOIN 来查询学生和他们所选的课程。 -- 使用 INNER JOIN 查询SELECTstudents.student_name,enrollments.course_nameFROMstudentsINNERJOINenrollmentsONstudents.student_id=enrollments.student_id; 1. 2. 3. 4. 说明: INNER JOIN:连接students和enrollments表,...
例如,如果我们向Customers表添加一个新的客户记录,但该客户尚未下任何订单,则该客户的信息不会出现在INNER JOIN的结果集中: INSERTINTOCustomers(firstName,lastName,email)VALUES('A','B','AB@example.com'); 1. 执行上述INSERT语句后进行INNER JOIN查询: SELECT*FROMCustomersINNERJOINOrdersONCustomers.customerID=...
To save time typing the table qualifiers, you can usetable aliasesin the query. For example, you can give theverylongtablenametable an aliasTand refer to its columns usingT.columninstead ofverylongtablename.column. Examples of using MySQL INNER JOIN clause Let’s take a look at two tables:...
-- 自然连接(去除等值连接的重复列) select * from customers natural join orders; -- 内连接 select customers.cust_id,orders.order_num from customers inner join orders on customers.cust_id = orders.cust_id; -- 左外连接 select customers.cust_id,orders.order_num from customers left outer join ...
1. Basic Inner Join sqlSELECTemployees.name,departments.department_nameFROMemployeesINNERJOINdepartmentsONemployees.department_id=departments.id; This example retrieves employee names along with their respective department names by joining the `employees` and `departments` tables on matching `department_id`...
a、内连接(inner join) 默认就是内连接,可省略inner。 只有数据存在时才能发送连接请求,即连接结果不能出现空行。 ON 表示连接条件,其条件表达式与 where 类似。 b、交叉连接(cross join) 没有条件的内连接。 如: select * from tb1 cross join tb2; c、外连接(outer join) 如果数据不存在,也会出现在连接...
INNER JOIN:返回两个表中满足连接条件的行。它是最常用的连接类型,只返回符合条件的匹配行。 LEFT JOIN(或LEFT OUTER JOIN):返回左表中所有的行,以及右表中满足连接条件的行。如果右表中没有匹配的行,结果集中将包含NULL值。 RIGHT JOIN(或RIGHT OUTER JOIN):与LEFT JOIN相反,返回右表中所有的行,以及左表中...
inner join:求两个表交集的数据。 使用inner join的示例如下: select o.id,o.code,u.name from order o inner join user u on o.user_id = u.id where u.status=1; 如果两张表使用inner join关联,mysql会自动选择两张表中的小表,去驱动大表,所以性能上不会有太大的问题。 使用left join的示例如...
MySQL LEFT JOIN Example The following SQL statement will select all customers, and any orders they might have: ExampleGet your own SQL Server SELECT Customers.CustomerName, Orders.OrderIDFROM CustomersLEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerIDORDER BY Customers.CustomerName; Note:...