1. 题目描述:git
表1: Person +-------------+---------+ | 列名 | 类型 | +-------------+---------+ | PersonId | int | | FirstName | varchar | | LastName | varchar | +-------------+---------+ PersonId 是上表主键 表2: Address +-------------+---------+ | 列名 | 类型 | +-------------+---------+ | AddressId | int | | PersonId | int | | City | varchar | | State | varchar | +-------------+---------+ AddressId 是上表主键 编写一个 SQL 查询,知足条件:不管 person 是否有地址信息,都须要基于上述两表提供 person 的如下信息: FirstName, LastName, City, State
2. 提交代码:github
# Write your MySQL query statement below select p.FirstName,p.LastName,a.City,a.State from Person as p left join Address as a on p.personId = a.personId;
3. 性能:性能
一样的代码,差距如此之大,code
github会员了解一下。哈哈blog
4. ....it