SQL-LEFT JOIN

Posted 2020-11-19 bashaowei

SQL LEFT JOIN 关键字：会从左表（table_name1）那里返回所有的行，即使在右表（table_name2）中并没有匹配的行。

其语法为：

select column_name from table_name1 LEFT JOIN table_name2 on table_name1.column_name=table_name2.column_name

举例：

select Persons.LastName, Persons.FirstName, Orders.OrderNo from Persons LEFT JOIN Orders on Persons.Id_P=Orders.Id_P order by Persons.LastName