qiubingcsdn的博客

给定一个Weather表，写一条SQL语句返回所有温度比前一天高的数据的Id+---------+------------------+------------------+| Id(INT) | RecordDate(DATE) | Temperature(INT) |+---------+------------------+------------------+| ...

错误的SQL代码SELECT Id FROM Weather AS W1, Weather AS W2WHERE W1.Id-W2.Id=1 AND W1.Temperature>W2.Temperature错误原因：SELECT Id的时候没有指定是W1表还是W2表，导致指代不明修改之后为SELECT W1.Id FROM Weather AS W1, Weath...

写SQL语句删除Person表中所有重复的邮箱数据，重复的邮箱只保留Id最小的邮箱数据+----+------------------+| Id | Email |+----+------------------+| 1 | john@example.com || 2 | bob@example.com || 3 | john@example.com...

假设一个网站有Customers和Orders两个表。写SQL语句查询所有没有下过订单的客户Table: Customers.+----+-------+| Id | Name |+----+-------+| 1 | Joe || 2 | Henry || 3 | Sam || 4 | Max |+----+-------+Table: Or...

写SQL语句查询Person表中所有重复的电子邮箱+----+---------+| Id | Email |+----+---------+| 1 | a@b.com || 2 | c@d.com || 3 | a@b.com |+----+---------+例如，你的语句对上表应该返回如下结果+---------+| Email |+---...

Employee表列出了包括经理在内的所有雇员，每一个雇员都有一个Id，同时表中存在一列ManagerId+----+-------+--------+-----------+| Id | Name | Salary | ManagerId |+----+-------+--------+-----------+| 1 | Joe | 70000 | 3 |...

写SQL查询语句获得Employee表中第二高的薪水+----+--------+| Id | Salary |+----+--------+| 1 | 100 || 2 | 200 || 3 | 300 |+----+--------+例如，给定如上Employee表，查询语句应该返回200作为它的第二高薪水。如果不存在第二高薪水就返回null...

Table: Person+-------------+---------+| Column Name | Type |+-------------+---------+| PersonId | int || FirstName | varchar || LastName | varchar |+-------------+---------+P...