mysql | 易学教程

Reduce database write on notification system or change approbate database?

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问题 We have a web app which requires to send lots of notifications to users (over 1,000,000 notifications per day). We use Laravel and MySQL for the database. I loop through a group of users send notifications and save it to the database. Let's say if I want to send a group of 1000 users. The data will be written to the DB 1000 time. As I said, we have over 1,000,000 notifications per day, which take so many resources. What's the appropriate way to approach this problem? I should change to a new

Lost connection to MySQL server during query - Python, MySql

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问题 I am trying to send INSERT statements to mysql from Python using pymysql. Based on some conditions if I find a particular file, I insert it's contents to it's corresponding table in database. Currently I have two tables CACCT and PAUTH. I have separate functions for table specific INSERTs. The functions are: 1. load_json_sql_CACCT() 2. load_json_sql_PAUTH() My main function is recon(). mysql_conn_dev = mysql.connect(host="xxxx", user="xxx", db="xxx") cur = mysql_conn_dev.cursor(mysql.cursors

Doctrine Query Language, Two joins query [closed]

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问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 5 years ago . Improve this question I have a problem with dql. I can't write properly query. Need to rewrite the query to dql 'SELECT Movie.title, Movie.price, Order.order_data, Order.order_status FROM (Order LEFT JOIN Order_has_Movie ON Order.order_id = Order_has_Movie.order_id) INNER JOIN Movie ON Order_has

面试MySQL，看这篇文章就够了！

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当游戏前端开发能力不断提升后，有的小伙伴已经开始不满足了，将魔爪伸向后端开发，立志做一个全栈游戏开发程序员！分享一篇MySQL的好文，加油吧！程序员！作者：zhangqh segmentfault.com/a/1190000012155267 一、EXPLAIN 做MySQL优化，我们要善用 EXPLAIN 查看SQL执行计划。下面来个简单的示例，标注(1,2,3,4,5)我们要重点关注的数据 type列，连接类型。一个好的sql语句至少要达到range级别。杜绝出现all级别 key列，使用到的索引名。如果没有选择索引，值是NULL。可以采取强制索引方式 key_len列，索引长度 rows列，扫描行数。该值是个预估值 extra列，详细说明。注意常见的不太友好的值有：Using filesort, Using temporary 二、SQL语句中IN包含的值不应过多 MySQL对于IN做了相应的优化，即将IN中的常量全部存储在一个数组里面，而且这个数组是排好序的。但是如果数值较多，产生的消耗也是比较大的。再例如： select id from table_name where num in(1,2,3) 对于连续的数值，能用 between 就不要用 in 了；再或者使用连接来替换。三、SELECT语句务必指明字段名称 SELECT *增加很多不必要的消耗（cpu、io

Java, changing boolean column to checkbox in jTable when using rs2xml for populating jTable

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问题 I am using a jTable which is populated with mysql db data using rs2xml table.setModel(DbUtils.resultSetToTableModel(rs)); I have some columns that are displayed by boolean values, but these must become checkboxes. I understand that i have to write my own AbstractTableModel, but I don't know how... Can one of you give an example of how you extend the AbstractTableModel and use it in your code? 回答1: I have some columns that are displayed by boolean values, but these must become checkboxes. Then

Meaning of this line: HAVING c2.hacker_id <> c.hacker.id?

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问题 I've been working on a HackerRank SQL question, "Challenges". This is the problem: Julia asked her students to create some coding challenges. Write a query to print the hacker_id, name, and the total number of challenges created by each student. Sort your results by the total number of challenges in descending order. If more than one student created the same number of challenges, then sort the result by hacker_id. If more than one student created the same number of challenges and the count is

How to INSERT string with single quote ' symbol [duplicate]

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问题 This question already has answers here : How can I prevent SQL injection in PHP? (28 answers) Closed 4 years ago . I want to do an INSERT into a MySQL database using: $sql = "INSERT INTO table (title1) VALUES ('$myVar')"; but the problem is $myVar can contain the single quotes ( ' symbols, e.g. in "idiot's"). Can somebody tell me how to handle any single quotes in the variable as a letter and not as a piece of code? (I know there are posts about this in the forum already, but I do not really

PHP面试-复习知识点整理

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false的七种情况整型0 浮点0.0 布尔false 空字符串'',"" 字符串'0' 空数组[] NULL 超全局数组 $GLOBALS，包含下面8个超全局数组的值 $_GET $_POST $_REQUERT，包含$_GET,$_POST,$_COOKIE $_SEESION $_COOKIE $_SERVER $_SERVER['SERVER_ADDR'] //服务器地址 $_SERVER['SERVER_NAME'] //服务名称 $_SERVER['REQUEST_TIME'] //请求时间 $_SERVER['QUERY_STRING'] //请求地址中问号后的内容 $_SERVER['HTTP_REFERER'] //上次请求地址 $_SERVER['HTTP_USER_AGENT'] //浏览器信息 $_SERVER['REMOTE_ARRR'] //客户端请求ip $_SERVER['REQUEST_URI'] // 请求中脚本名称 $_SERVER['PATH_INFO'] // 请求中路径 $_FIELS $_ENV null的三种情况直接赋值NULL 未定义变量 unset销毁后的变量常量一定定义，不可删除和修改 const 更快，是语言结构，可定义类常量 define 是函数预定义常量 FILE 文件所在路径+文件名 LINE 所在代码行

分享5个免费的在线 SQL 数据库环境，简直太方便了！

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关注我们, 设为星标,每天7:30不见不散,架构路上与您共享回复" 架构师 "获取资源今天给大家分享几个在线的免费 SQL 运行环境，也就是在线数据库。这些网站可以帮助我们快速运行一些 SQL 语句的测试或者验证，同时还可以在网络上进行分享，关键不需要自己安装数据库。 SQL Fiddle SQL Fiddle 提供了 MySQL、Oracle、PostgreSQL、SQLite 以及 SQL Server 数据库环境，使用时无需注册。其中，左侧文本框用于输入初始化语句创建表结构和数据，点击“Build Schema📥”运行；也可以通过“Text to DDL”将格式化文本转换为 DDL 语句。右侧文本框用于输入 SQL 语句，点击“Run SQL▶️”执行，执行结果显示在页面下方；“Run SQL▶️”可以选择输出结果的格式，包括表格、普通文本以及 Markdown 三种格式。另外，复制网页地址可以分享本次测试的数据和结果，以上截图的地址为：http://sqlfiddle.com/#!9/a6c585/1。 DB Fiddle DB Fiddle 提供了 MySQL、PostgreSQL 以及 SQLite 数据库的最新版本，使用时无需注册，同时也提供了付费版本。其中，最左侧文本框可以输入本次测试的标题和描述。中间文本框用于输入初始化语句，点击“▶️Run

分享5个免费的在线 SQL 数据库环境，简直太方便了！

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点击上方蓝色“ 程序猿DD ”，选择“设为星标” 回复“ 资源 ”获取独家整理的学习资料！作者 | 不剪发的Tony老师来源 | blog.csdn.net/horses/article/details/108603935 大今天给大家分享几个在线的免费 SQL 运行环境，也就是在线数据库。这些网站可以帮助我们快速运行一些 SQL 语句的测试或者验证，同时还可以在网络上进行分享，关键不需要自己安装数据库。 SQL Fiddle SQL Fiddle 提供了 MySQL、Oracle、PostgreSQL、SQLite 以及 SQL Server 数据库环境，使用时无需注册。 SQL Fiddle 其中，左侧文本框用于输入初始化语句创建表结构和数据，点击“Build Schema📥”运行；也可以通过“Text to DDL”将格式化文本转换为 DDL 语句。右侧文本框用于输入 SQL 语句，点击“Run SQL▶️”执行，执行结果显示在页面下方；“Run SQL▶️”可以选择输出结果的格式，包括表格、普通文本以及 Markdown 三种格式。另外，复制网页地址可以分享本次测试的数据和结果，以上截图的地址为：http://sqlfiddle.com/#!9/a6c585/1。地址：http://sqlfiddle.com/ DB Fiddle DB Fiddle 提供了

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