技能补全计划：CSS

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/*标签选择器*/
p {
    color: red;
    font-size: 12px;
}

题目

编写一个 SQL 查询，获取 Employee 表中第二高的薪水（Salary） 。

例如上述 Employee 表，SQL查询应该返回 200 作为第二高的薪水。如果不存在第二高的薪水，那么查询应返回 null。

题目

编写一个 SQL 查询，获取 Employee 表中第n高的薪水（Salary） 。

例如上述 Employee 表，n = 2 时，应返回第二高的薪水 200。如果不存在第 n 高的薪水，那么查询应返回 null。

题目

Write a SQL query to rank scores. If there is a tie between two scores, both should have the same ranking. Note that after a tie, the next ranking number should be the next consecutive integer value. In other words, there should be no "holes" between ranks.

For example, given the above Scores table, your query should generate the following report (order by highest score):

Write a SQL query to find all numbers that appear at least three times consecutively.

For example, given the above Logs table, 1 is the only number that appears consecutively for at least three times.

题解

题目

The Employee table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id.

Given the Employee table, write a SQL query that finds out employees who earn more than their managers. For the above table, Joe is the only employee who earns more than his manager.

题目

Write a SQL query to find all duplicate emails in a table named Person.

For example, your query should return the following for the above table:

题目

Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything.

Using the above tables as example, return the following:

题目

The Employee table holds all employees. Every employee has an Id, a salary, and there is also a column for the department Id.

The Department table holds all departments of the company.

题目

The Employee table holds all employees. Every employee has an Id, and there is also a column for the department Id.

The Department table holds all departments of the company.