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App Inventor 2 低功耗蓝牙(BLE) 硬件接入、数据通信及IO控制 · App Inventor 2 中文网
...本文主要介绍一款较为通用、价格低廉的BLE设备从零开始如何利用App Inventor 2开发一款自己专属的手机蓝牙App应用。
BLE与经典蓝牙的区别可参考：《低功耗蓝牙(BLE) 和 经典蓝牙(SPP) 的区别》。
本文主要通过一款常见的BLE硬件...
Create new user in MySQL and give it full access to one database
I want to create a new user in MySQL and give it full access only to one database, say dbTest , that I create with a command like create database dbTest; . What would be the MySQL commands to do that?
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Can't connect to local MySQL server through socket '/var/mysql/mysql.sock' (38)
I am having a big problem trying to connect to mysql. When I run:
41 Answers
41
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MySQL show status - active or total connections?
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Connections
The number of connection attempts (successful or not) to the MySQL server.
You can see the number of active connections either through the Threads_connected status variable:
Threads_connected
The number of currently open connections.
mysql> show status where `variable_name` = 'Th...
App Inventor 2 多用户预订系统如何设计？ - App Inventor 2 中文网 - 清泛...
问：我遇到了一个难题，我开发了一个软件，两个手机都安装了同一个软件，我在一个手机上显示按钮已经不能启用，但在另一个手机上该按钮确还能用，我的目标是这个跟酒店房间一样，当某个房间有人订了，其他人就不能订...
PHP连接MySQL报错：Fatal error: Call to undefined function mysql_connec...
【问题描述】
PHP测试连接MySQL的程序如下：
<?php
$host='localhost';
$user_name='root';
$password='mysql';
$conn=mysql_connect($host,$user_name,$password);
if (!$conn)
{
die('数据库连接失败：'.mysql_error());
}
echo '数据库连接成功！';
if (mysql_clos...
PDOException SQLSTATE[HY000] [2002] No such file or directory
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The error message indicates that a MySQL connection via socket is tried (which is not supported).
In the context of Laravel (artisan), you probably want to use a different / the correct environment. Eg: php artisan migrate --env=production (or whatever enviro...
What is the most efficient/elegant way to parse a flat table into a tree?
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Now that MySQL 8.0 supports recursive queries, we can say that all popular SQL databases support recursive queries in standard syntax.
WITH RECURSIVE MyTree AS (
SELECT * FROM MyTable WHERE ParentId IS NULL
UNION ALL
SELE...
MongoDB与内存 - 大数据 & AI - 清泛网 - 专注IT技能提升
...于它对内存的贪得无厌，至于个中缘由，我先讲讲Linux是如何管理内存的，再说说MongoDB是如何使用内存的...但凡初次接触MongoDB的人，无不惊讶于它对内存的贪得无厌，至于个中缘由，我先讲讲Linux是如何管理内存的，再说说MongoD...
MongoDB与内存 - 大数据 & AI - 清泛网 - 专注IT技能提升
...于它对内存的贪得无厌，至于个中缘由，我先讲讲Linux是如何管理内存的，再说说MongoDB是如何使用内存的...但凡初次接触MongoDB的人，无不惊讶于它对内存的贪得无厌，至于个中缘由，我先讲讲Linux是如何管理内存的，再说说MongoD...