原创 eclipse安裝maven插件失敗的解決辦法
在工作中，需要用到maven。在安裝好maven後，在eclipse中安裝maven插件時，卻遇到了問題，總是提示安裝失敗。提示信息如下： Cannot complete the install because one ormore re
2020-07-05 17:24:21
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原创 eclipse打包maven工程文件提示找不到tools.jar的解決辦法
在用eclipse打包maven工程文件時，出現以下錯誤：tools.jar not found，如下圖所示： 問題分析： 出現這個原因是因爲Eclipse默認是運行在jre上的，而tools.jar存在於jdk目錄下的。如果默認配置
2020-07-05 17:24:21
原创 【leetcode Database】177. Nth Highest Salary
題目： Write a SQL query to get the nth highest salary from the Employee table. +----+--------+ | Id | Salary | +----+--
2020-07-05 17:24:21
原创 【leetcode Database】196. Delete Duplicate Emails
題目： Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails base
2020-07-05 17:24:21
1
原创 【leetcode Database】181. Employees Earning More Than Their Managers
題目： The Employee table holds all employees including their managers. Every employee has an Id, and there is also a c
2020-07-05 17:24:21
原创 【leetcode Database】185. Department Top Three Salaries
題目： The Employee table holds all employees. Every employee has an Id, and there is also a column for the department
2020-07-05 17:24:21
原创 【leetcode Database】180. Consecutive Numbers
題目： Write a SQL query to find all numbers that appear at least three times consecutively. +----+-----+ | Id | Num | +
2020-07-05 17:24:21
原创 Java編程風格
來自《The Elementsof Java Style》-《Java編程風格》一書，值得一讀的書籍，會讓你在細節上節省很多時間，合作之間更加愉快！ 好處不多說了，但是有幾個原則如下： 1.保持原有風格 2.堅持最小驚奇原則 3.第一次就
2020-02-21 02:34:44
原创 【leetcode Database】183. Customers Who Never Order
題目： Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find
2020-02-21 02:34:44
1
原创 【mysql學習筆記】-explain的用法
1.explain的使用方法 mysql中的explain命令顯示了mysql如何使用索引來處理select語句以及連接表。使用時直接在select語句前加上explain就行了。例子如下： explain select * from o
2020-02-21 02:34:44
原创 瀏覽器訪問tomcat服務器時提示out of memory error
今天在啓動tomcat服務器後，在瀏覽器請求網頁時，總是出現500錯誤，顯示java.lang.OutOfMemoryError: PermGen space。 出錯原因如下：PermGen space的全稱是Permanent Gene
2020-02-21 02:34:34
原创 【leetcode Database】184. Department Highest Salary
題目： The Employee table holds all employees. Every employee has an Id, a salary, and there is also a column for the d
2020-02-21 02:34:34
1
原创 【leetcode Database】197. Rising Temperature
題目： Given a Weather table, write a SQL query to find all dates' Ids with higher temperature compared to its previous
2020-02-21 02:34:34
原创 【leetcode Database】182. Duplicate Emails
題目： Write a SQL query to find all duplicate emails in a table named Person. +----+---------+ | Id | Email | +----+-
2020-02-21 02:34:34
原创 【leetcode Database】176. Second Highest Salary
題目： Write a SQL query to get the second highest salary from the Employee table. +----+--------+ | Id | Salary | +----
2020-02-21 02:34:34