1. 程式人生 > >【leetcode】sql練習題

【leetcode】sql練習題

題目描述: 表1: Person:

+-------------+---------+
| 列名         | 型別     |
+-------------+---------+
| PersonId    | int     |
| FirstName   | varchar |
| LastName    | varchar |
+-------------+---------+
PersonId 是上表主鍵

表二:Address

+-------------+---------+
| 列名         | 型別    |
+-------------+---------+
| AddressId | int | | PersonId | int | | City | varchar | | State | varchar | +-------------+---------+ AddressId 是上表主鍵

編寫一個 SQL 查詢,滿足條件:無論 person 是否有地址資訊,都需要基於上述兩表提供 person 的以下資訊:

FirstName, LastName, City, State

此處使用關聯查詢,因為一邊為null,另一邊也要顯示,所以不能使用內連線inner join,可以使用左右連線:

# 右連線
select p.FirstName,p.LastName,a.City,a.State from Address as a right join Person as p on p.personId = a.personId

# 左連線
select p.FirstName,p.LastName,a.City,a.State from Person as p left join Address as a on p.personId = a.personId