之前找工作的时候，我的目标是找互联网、电商方面的公司开发工作，但是碰了好多壁。原因是一直做企业级开发，与互联网开发方面不对口。而互联网公司都需要有互联网开发经验的，对这方面我有很大的不足。 一次在面试的过程中我就问面试官，互联网现在一般用哪
之前找工作的时候，我的目标是找互联网、电商方面的公司开发工作，但是碰了好多壁。原因是一直做企业级开发，与互联网开发方面不对口。而互联网公司都需要有互联网开发经验的，对这方面我有很大的不足。
一次在面试的过程中我就问面试官，互联网现在一般用哪些技术，他告诉我现在互联网开发主要是针对大数据的处理，云计算的方向。具体点的就是hadoop、hbase、高并发、网络编程方面的。
所以最近我准备学习hadoop的应用，在此留下我学习的足迹。
先上一段百度百科对hadoop的介绍：
hadoop：
|
一个分布式系统基础架构，由Apache基金会所开发。 用户可以在不了解分布式底层细节的情况下，开发分布式程序。充分利用集群的威力进行高速运算和存储。 [1] Hadoop实现了一个分布式文件系统（Hadoop Distributed File System），简称HDFS。HDFS有高容错性的特点，并且设计用来部署在低廉的（low-cost）硬件上；而且它提供高吞吐量（high throughput）来访问应用程序的数据，适合那些有着超大数据集（large data set）的应用程序。HDFS放宽了（relax）POSIX的要求，可以以流的形式访问（streaming access）文件系统中的数据。 Hadoop的框架最核心的设计就是：HDFS和MapReduce.HDFS为海量的数据提供了存储，则MapReduce为海量的数据提供了计算。[2] |
声明: 本文采用 BY-NC-SA 协议进行授权 | yu博客
转载请注明转自《hadoop学习-前记》
Detailed explanation of the installation steps of MySQL on macOS systemApr 29, 2025 pm 03:36 PMInstalling MySQL on macOS can be achieved through the following steps: 1. Install Homebrew, using the command /bin/bash-c"$(curl-fsSLhttps://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)". 2. Update Homebrew and use brewupdate. 3. Install MySQL and use brewinstallmysql. 4. Start MySQL service and use brewservicesstartmysql. After installation, you can use mysql-u
How to use conditional filtering and grouping in MySQL queryApr 29, 2025 pm 03:33 PMIn MySQL, conditional filtering is implemented through the WHERE clause and grouping is completed through the GROUPBY clause. 1. Use the WHERE clause to filter data, such as finding employees with salary above 5,000. 2. Use the GROUPBY clause to group and aggregate data, such as counting the number of employees by department. 3. Choose the appropriate index to optimize query performance and avoid using functions or expressions as WHERE conditions. 4. Combining subqueries and EXPLAIN commands improve the efficiency of complex queries.
How to clear MySQL table data but preserve table structureApr 29, 2025 pm 03:30 PMIn MySQL, clearing table data but preserving table structure can be implemented through the TRUNCATETABLE and DELETE commands. 1. The TRUNCATETABLE command quickly deletes all records and resets the self-increment column. 2. The DELETE command deletes data line by line, does not reset the self-increment column, and can delete specific records in combination with the WHERE clause.
Methods to deduplicate MySQL query resultsApr 29, 2025 pm 03:27 PMDeduplication in MySQL mainly uses DISTINCT and GROUPBY. 1.DISTINCT is used to return unique values, such as SELECTDISTINCTname, ageFROMusers. 2. GROUPBY realizes deduplication through grouping and can perform aggregation operations, such as SELECTid, name, MAX(created_at)aslatest_dateFROMusersGROUPBYname.
How to view information about all databases in MySQLApr 29, 2025 pm 03:24 PMViewing the information of all databases in MySQL can be achieved in two ways: 1. Use the SHOWDATABASES; command to quickly list all database names. 2. Query the INFORMATION_SCHEMA.SCHEMATA table to obtain more detailed information, such as the database creation time and character set settings.
How to add and delete unique constraints to MySQL tablesApr 29, 2025 pm 03:21 PMIn MySQL, you can add and delete unique constraints through the following steps: 1. Add unique constraints when creating a table, using the CREATETABLE statement; 2. Add unique constraints on existing tables, using the ALTERTABLE and ADDCONSTRAINT statements; 3. Delete unique constraints, using the ALTERTABLE and DROPINDEX statements. Unique constraints ensure that the values of a column or columns in the table are unique, prevent data duplication, and maintain data integrity.
How to copy table structure and data in MySQLApr 29, 2025 pm 03:18 PMThe methods of copying table structure and data in MySQL include: 1. Use CREATETABLE...LIKE to copy the table structure; 2. Use INSERTINTO...SELECT to copy the data. Through these steps, data backup and migration can be efficiently performed in different scenarios.
How to get data randomly from MySQL tableApr 29, 2025 pm 03:15 PMRandomly fetching data from MySQL tables can be done using the RAND() function. 1. Basic usage: SELECTFROMusers ORDERBYRAND()LIMIT5; 2. Advanced usage: SELECTFROMusersWHEREid>=(SELECTFLOOR(RAND()*(SELECTMAX(id)FROMusers)))LIMIT5; Optimization strategy includes using index and pagination query.
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Atom editor mac version download
The most popular open source editor
DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software
VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft
MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.
Zend Studio 13.0.1
Powerful PHP integrated development environment
