在 SQL 中,外连接主要有三种类型:左外连接(LEFT JOIN)、右外连接(RIGHT JOIN)和全外连接(FULL OUTER JOIN)。LEFT JOIN 会返回左表中的所有记录以及右表中匹配的记录;RIGHT JOIN 则相反,返回右表中的所有记录和左表中匹配的记录;FULL OUTER JOIN 则返回两个表中的所有记录。如果某一表中没有匹配项,结果中...
-- Usingimplicitjoin (listing multiple tables)SELECTs.description FROM Documents d, Statuses sWHEREd.statusId = s.id AND d.id =9; -- Using INNER JOINSELECTs.description FROM Documents d INNER JOIN Statuses s ON d.statusId = s.idWHEREd.id =9; 第二种方法的好处是它有助于将连接条件(on...
8-Outer Join Between Multiple Tables 多表外连接 9-Self Outer Joins自外连接 10-the USING Clause 子句 11-Natural Joins自然连接 12-Cross Joins交叉连接 13-Unions 联合 在多张表格中检索数据 1-Inner Joins 内连接 / JOIN ON customers 和 orders在不同表格 因为customers的地址、手机会经常更改,如果orders...
usesql_store;selecto.order_id,o.order_date,c.first_name,c.last_name,os.nameasstatusfromordersojoincustomerscono.customer_id=c.customer_idjoinorder_statusesosono.status=os.order_status_id 结果如下: 小结:join多个表格只需要一直写join、join、join 有时候同一件产品(product_id)会有不同的size,类...
多表查询(Displaying Data from Multiple Tables): JOIN: SQL 的连接(JOIN)语句将数据库中的两个或多个表组合起来,由"连接"生成的集合, 可以被保存为表, 或者当成表来使用. JOIN 语句的含义是把两张表的属性通过它们的值组合在一起. 基于ANSI 标准的 SQL 列出了四种 JOIN 方式: 内连接(INNER), 外连接(OU...
SQL Inner Join – How to Join 3 Tables in SQL and MySQL If you're dealing with a database, it's possible that you will have to gather information from multiple tables. This guide will demonstrate the process. Although I have previously covered SQL joins in two separate articles, let's ...
表名1 left outer join 表名2 on 连接条件 表名1 right outer join 表名2 on 连接条件 表名1 full outer join 表名2 on 连接条件 其中的outer可以省去不写 查询s_emp表中每一个员工的名字和部门编号 select last_name,dept_id from s_emp
SQL INNER JOIN Summary: in this tutorial, you will learn how to query data from multiple tables usingSQL INNER JOINstatement. In the previous tutorial, you learned how to query data from a single table using theSELECT statement. However, you often want to query data from multiple tables to...
which is much more cumbersome. In essence, table aliases make the entire SQL statement easier to understand, especially when multiple tables are included. An alternative way to specify a join between tables is to use theJOINandONkeywords. In the current example, the SQL query would be, ...
JOIN Multiple Tables We can also join more than two tables using JOIN. For example, -- join three tables: Customers, Orders, and Shippings SELECT Customers.first_name, Orders.item, Shippings.status FROM Customers JOIN Orders ON Customers.customer_id = Orders.customer_id JOIN Shippings ON Cus...