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[LeetCode]Customers Who Never Order
作者是 发布于 在 LeetCode.

题目描述：

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.

Table: Customers.

+----+-------+
| Id | Name  |
+----+-------+
| 1  | Joe   |
| 2  | Henry |
| 3  | Sam   |
| 4  | Max   |
+----+-------+

Table ...

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[LeetCode]Binary Tree Postorder Traversal
作者是 发布于 在 LeetCode.

题目描述：

Given a binary tree, return the postorder traversal of its nodes' values.

For example:
Given binary tree {1,#,2,3},
   1
    \
     2
    /
   3
return [3,2,1].

Note: Recursive solution is trivial, could you do it iteratively?

题目大意：

非递归实现二叉树的后序遍历 ...

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[LeetCode]Binary Tree Inorder Traversal
作者是 发布于 在 LeetCode.

题目描述：

Given a binary tree, return the inorder traversal of its nodes' values.

For example:
Given binary tree {1,#,2,3},
   1
    \
     2
    /
   3
return [1,3,2].

Note: Recursive solution is trivial, could you do it iteratively?

题目大意：

非递归实现二叉树的中序遍历 ...

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[LeetCode]Duplicate Emails
作者是 发布于 在 LeetCode.

题目描述：

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

+----+---------+
| Id | Email   |
+----+---------+
| 1  | a@b.com |
| 2  | c@d.com |
| 3  | a@b.com |
+----+---------+
For example, your query should return the following for the above ...

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[LeetCode]Employees Earning More Than Their Managers
作者是 发布于 在 LeetCode.

题目描述：

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 ...

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