JavaScript | js - html & nbsp 结构化css & nbsp 样式javascript & nbsp | SQL Database library
kandi X-RAY | JavaScript Summary
kandi X-RAY | JavaScript Summary
html 结构化css 样式javascript 行为交互 01.javascript基础 02.javascript操作bom对象 03.javascript操作dom对象 04.javascript的面向对象-------------------------------------- 05.jquery (js) .css .js 06.jquery选择器 * 07.jquery事件和动画 08.jquery操作dom对象 09.表单验证 10.表单验证的框架 jquery validate11.bootstrap 封装了html css js. javascript基础 (livescript) 01.和java的关系,只是借势! 02.是一个脚本语言,以.js结尾 03.浏览器编译javascript,解析器我们称之为javascript引擎! 04.无需预编译 js是一种弱语言类型 var a=10; var a="101"; var a=new date(); 05.运行在客户端 减轻服务器的压力. 目的: 01.提升用户的体验 02.减轻服务器的压力 组成部分: 01.ecmascript规定了js的基本语法和基本对象 02.bom(浏览器对象模型) 提供了处理网页内容的方法和接口 03.dom(文档对象模型) 提供了与浏览器进行交互的方法和接口 我们一个页面中可以引入css文件还可以引入js文件? 有没有顺序呢? 01.css写在head中02.js文件的引入写在body的最下方. js的引入方式:01.行内引入02.内部引入03.外部引入 js中的常用事件 01.不想让a超链接 立即跳转至指定的页面 02.想让用户点击的时候 做一些处理工作 javascript: 伪协议 01.先去执行js代码 02.根据js代码做操作 alert('就是不跳转') 后续会换成某个操作的函数(方法) 跳转 伪协议 javascript:onclick 点击事件onblur 失去焦点事件onfocus 获取焦点事件. js数据类型 undefined: 声明但是没有赋予初始值!没有被定义的变量! var name; alert(name); //什么都没有 alert(typeof(name)); //undefined number: 包含了整数和浮点数 typeof(20) typeof(20.2) string : 被单引号和双引号括起来的内容都是字符串 typeof('20') typeof('20.2') boolean: true 和 false alert(typeof(true)); //把true 当成一个变量名 alert(typeof(true)); //√ alert(typeof("true")); //string object: js中的对象,包含数组, null和对象! null:空值,表示对象不存在,等于undefined! typeof 检测变量的数据类型01. typeof 空格变量名称02. typeof(变量名称) 类型转换parseint(): 变量值可以不是一个数字,返回第一个不为数字的所有值, 返回一个整数! 否则返回nan(not a number)parsefloat():返回一个浮点数! 强制类型转换 number():把变量整体当作转换的值,如果有一个字符不是数值,则返回nan! boolean():只要变量不是false,0,undefined,null,nan,未定义的参数或者定义未赋值 空串,或者什么都没有输入! 其他都返回true! == 和 === == :在两个变量比较的时候,先进行类型转换,之后再比较!alert("0"==false);首先会把字符串"0"转换成number 0false转换成number 00==0 ===:比较严格,先比较两个变量的类型是否一致,之后再比较值!不会类型转换! 注意点:01.如果比较的变量中boolean的值,会先把boolean类型的值转换成number类型!02.如果比较的变量中string的值,会先把string类型的值转换成number类型! 输入和确认alert(): 只有一个确定按钮!confirm ():是一个提示框,有确定和取消按钮! 用户点击确定返回值是true 用户点击取消返回值是false prompt():是一个对话框! 01.第一参数是提示语句 02.第二参数是输入框中的默认值,可以省略返回值是我们第二个参数(用户的输入)! js中也有选择结构!和java中的用法一致! 数组 var arr1=new array(); //没有长度var arr1=new array(5); //有长度5var arr1=new array(1,2,3,4,5) //定义数组的同时赋值var arr1=[1,2,3]; 向数组中新增元素 push把数组中的每个元素使用指定的分隔符连接起来,变成字符串! join 循环 for in for(var index in arrs){ document.write(arrs[index])}index 是元素的下标! 函数 定义函数的两种方式跳转 function sayhello(username){ alert(username+"辛苦了!"); } var sayhello=function(username){ alert(username+"辛苦了!"); } javascript操作 bom对象 bom对象(浏览器对象模型 browser object
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Trending Discussions on SQL Database
QUESTION
Not really sure what caused this but most likely exiting the terminal while my rails server which was connected to PostgreSQL database was closed (not a good practice I know but lesson learned!)
I've already tried the following:
- Rebooting my machine (using MBA M1 2020)
- Restarting PostgreSQL using homebrew
brew services restart postgresql
- Re-installing PostgreSQL using Homebrew
- Updating PostgreSQL using Homebrew
- I also tried following this link but when I run
cd Library/Application\ Support/Postgres
terminal tells me Postgres folder doesn't exist, so I'm kind of lost already. Although I have a feeling that deleting postmaster.pid would really fix my issue. Any help would be appreciated!
ANSWER
Answered 2022-Jan-13 at 15:19My original answer only included the troubleshooting steps below, and a workaround. I now decided to properly fix it via brute force by removing all clusters and reinstalling, since I didn't have any data there to keep. It was something along these lines, on my Ubuntu 21.04 system:
QUESTION
I am using Go's MongodDB driver (https://pkg.go.dev/go.mongodb.org/mongo-driver@v1.8.0/mongo#section-documentation) and want to obtain the version of the mongoDB server deployed.
For instance, if it would been a MySQL database, I can do something like below:
...ANSWER
Answered 2022-Mar-26 at 08:04The MongoDB version can be acquired by running a command, specifically the buildInfo
command.
Using the shell, this is how you could do it:
QUESTION
What am I trying to do?
Django does not support setting enum data type in mysql database. Using below code, I tried to set enum data type.
Error Details
_mysql.connection.query(self, query) django.db.utils.ProgrammingError: (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'NOT NULL,
created_at
datetime(6) NOT NULL,user_id
bigint NOT NULL)' at line 1")
Am I missing anything?
Enumeration class with all choices
...ANSWER
Answered 2021-Sep-29 at 19:39You can print out the sql for that migration to see specifically whats wrong, but defining db_type
to return "enum"
is definitely not the right way to approach it.
QUESTION
I am having difficulties to scaffold an existing MySQL database using EF core. I have added the required dependencies as mentioned in the oracle doc:
...ANSWER
Answered 2021-Dec-12 at 10:11I came across the same issue trying to scaffold an existing MySQL database. It looks like the latest version of MySql.EntityFrameworkCore (6.0.0-preview3.1) still uses the EFCore 5.0 libraries and has not been updated to EFCore 6.0.
It also seems Microsoft.EntityFrameworkCore.Diagnostics was last implemented in EFCore 5 and removed in 6.
When I downgraded all the packages to the 5 version level, I was able to run the scaffold command without that error.
QUESTION
I'm using Lambda with RDS Proxy to be able to reuse DB connections to a MySQL database.
Should I close the connection after executing my queries or leave it open for the RDS Proxy to handle?
And if I should close the connection, then what's the point of using an RDS Proxy in the first place?
Here's an example of my lambda function:
...ANSWER
Answered 2021-Dec-11 at 18:10The RDS proxy sits between your application and the database & should not result in any application change other than using the proxy endpoint.
Should I close the connection after executing my queries or leave it open for the RDS Proxy to handle?
You should not leave database connections open regardless of if you use or don't use a database proxy.
Connections are a limited and relatively expensive resource.
The rule of thumb is to open connections as late as possible & close DB connections as soon as possible. Connections that are not explicitly closed might not be added or returned to the pool. Closing database connections is being a good database client.
Keep DB resources tied up with many open connections & you'll find yourself needing more vCPUs for your DB instance which then results in a higher RDS proxy price tag.
And if I should close the connection, then what's the point of using an RDS Proxy in the first place?
The point is that your Amazon RDS Proxy instance maintains a pool of established connections to your RDS database instances for you - it sits between your application and your RDS database.
The proxy is not responsible for closing local connections that you make nor should it be.
It is responsible for helping by managing connection multiplexing/pooling & sharing automatically for applications that need it.
An example of an application that needs it is clearly mentioned in the AWS docs:
Many applications, including those built on modern serverless architectures, can have a large number of open connections to the database server, and may open and close database connections at a high rate, exhausting database memory and compute resources.
To prevent any doubt, also feel free to check out an AWS-provided example that closes connections here (linked to from docs), or another one in the AWS Compute Blog here.
QUESTION
I have a PostgreSQL database hosted on Heroku which is throwing me this error that I can't wrap my head around.
...ANSWER
Answered 2022-Feb-13 at 22:21AUTOINCREMENT
is not a valid option for CREATE TABLE
in Postgres
You can use SERIAL
or BIGSERIAL
:
QUESTION
Our stack is nodejs with MySQL we're using MySQL connections pooling our MySQL database is managed on AWS aurora . in case of auto failover the master DB is changed the hostname stays the same but the connections inside the pool stays connected to the wrong DB. The only why we found in order to reset the connection is to roll our servers.
this is a demonstration of a solution I think could solve this issue but I prefer a solution without the set interval
...ANSWER
Answered 2022-Feb-04 at 12:22Instead of manually monitoring the DB health, as you have also hinted, ideally we subscribe to failover events published by AWS RDS Aurora.
There are multiple failover events listed here for the DB cluster: Amazon RDS event categories and event messages
You can use and test to see which one of them is the most reliable in your use case for triggering poolCluster.end()
though.
QUESTION
I am trying to run a server with a MySQL Database, however I keep getting this huge error and I am not sure why.
...ANSWER
Answered 2021-Aug-11 at 14:38Maybe a solution. Source : https://dba.stackexchange.com/questions/8239/how-to-easily-convert-utf8-tables-to-utf8mb4-in-mysql-5-5
Change your CHARACTER SET AND COLLATE to utf8mb4.
For each database:
QUESTION
I am following this tutorial on migrating data from an oracle database to a Cloud SQL PostreSQL instance.
I am using the Google Provided Streaming Template Datastream to PostgreSQL
At a high level this is what is expected:
- Datastream exports in Avro format backfill and changed data into the specified Cloud Bucket location from the source Oracle database
- This triggers the Dataflow job to pickup the Avro files from this cloud storage location and insert into PostgreSQL instance.
When the Avro files are uploaded into the Cloud Storage location, the job is indeed triggered but when I check the target PostgreSQL database the required data has not been populated.
When I check the job logs and worker logs, there are no error logs. When the job is triggered these are the logs that logged:
...ANSWER
Answered 2022-Jan-26 at 19:14This answer is accurate as of 19th January 2022.
Upon manual debug of this dataflow, I found that the issue is due to the dataflow job is looking for a schema with the exact same name as the value passed for the parameter databaseName
and there was no other input parameter for the job using which we could pass a schema name. Therefore for this job to work, the tables will have to be created/imported into a schema with the same name as the database.
However, as @Iñigo González said this dataflow is currently in Beta and seems to have some bugs as I ran into another issue as soon as this was resolved which required me having to change the source code of the dataflow template job itself and build a custom docker image for it.
QUESTION
I have to move a large Odoo(v13) database almost 1.2TB(DATABASE+FILESTORE), I can't use the UI for that(keeps loading for 10h+ without a result) and I dont want to only move postgresql database so I need file store too, What should I do? extract db and copy past the filestore folder? Thanks a lot.
...ANSWER
Answered 2022-Jan-14 at 16:59You can move database and filestore separately. Move your Odoo PostgreSQL database with normal Postgres backup/restore cycle (not the Odoo UI backup/restore), this will copy the database to your new server. Then move your Odoo filestore to new location as filesystem level copy. This is enough to get the new environment running.
I assume you mean moving to a new server, not just moving to a new location on same filesystem on the same server.
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