add leetcode

Author: wave-gbt

Database/175. Combine Two Tables.md

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+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.
+```
+Write a SQL query for a report that provides the following information for each person in the Person table, regardless if there is an address for each of those people:
+
+```
+FirstName, LastName, City, State
+```
+
+**SQL**
+```
+select a.FirstName, a.LastName, b.City, b.State
+from person a left join  Address b 
+on a.PersonId = b.PersonId
+```

Database/181. Employees Earning More Than Their Managers.md

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+The `Employee` table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id.
+
+```
++----+-------+--------+-----------+
+| Id | Name  | Salary | ManagerId |
++----+-------+--------+-----------+
+| 1  | Joe   | 70000  | 3         |
+| 2  | Henry | 80000  | 4         |
+| 3  | Sam   | 60000  | NULL      |
+| 4  | Max   | 90000  | NULL      |
++----+-------+--------+-----------+
+```
+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.
+
+```
++----------+
+| Employee |
++----------+
+| Joe      |
++----------+
+
+```
+
+**SQL**
+```
+select a.name as Employee 
+from Employee a,
+     Employee b
+where a.managerId = b.Id
+ and a.salary > b.salary
+```