Table: Person
+-------------+---------+ | Column Name | Type | +-------------+---------+ | PersonId | int | | FirstName | varchar | | LastName | varchar | +-------------+---------+ PersonId is the primary key column for this table.
Table: Address
+-------------+---------+ | Column Name | Type | +-------------+---------+ | AddressId | int | | PersonId | int | | City | varchar | | State | varchar | +-------------+---------+ AddressId is the primary key column for this table.
为报表编写一个SQL查询,为Person表中的每个人提供以下信息,而不管这些人是否有地址:
FirstName ,LastName,City ,State
根据条件不管这些人是否有地址,如果用inner join 那么在地址表中,没用地址的人们将不会出现结果中。所以用左外连接。
select p.FirstName,p.lastname,a.city,a.state from person p left join address a on p.personId = a.personId
因为查询字段在两张表中是唯一的,所以可以省略表前缀,写成
select FirstName ,LastName ,city ,state from person left join address on Person.personId = address.personId