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Possible to do a MySQL foreign key to one of two possible tables?
...ut logical XOR is not standard SQL and is not supported by all SQL brands. MySQL has it, but PostgreSQL does not. Oracle has it, but Microsoft does not until 2016. And so on.
– Bill Karwin
Aug 19 '15 at 15:09
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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...
Optimal way to concatenate/aggregate strings
...com/en-us/sql/t-sql/functions/string-agg-transact-sql
GROUP_CONCAT() in MySQL
http://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_group-concat
(Thanks to @Brianjorden and @milanio for Azure update)
Example Code:
select Id
, STRING_AGG(Name, ', ') Names
from Demo
group by I...
App Inventor 2 人脸识别App开发 - 第三方API接入的通用方法 · App Inventor 2 中文网
...建一个应用以获得API调用时必要的api_key及api_secret。
如何理解api_key及api_secret：可以类比为 API Key是用户ID（用于标识用户），Secret Key是密码（用于鉴权）。“你需要两个不同的密钥，一个告诉他们你是谁，另一个证明你就是...
Is there a REAL performance difference between INT and VARCHAR primary keys?
...e performance difference between using INT vs. VARCHAR as a primary key in MySQL? I'd like to use VARCHAR as the primary key for reference lists (think US States, Country Codes) and a coworker won't budge on the INT AUTO_INCREMENT as a primary key for all tables.
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How can I import a database with MySQL from terminal?
How can I import a database with mysql from terminal?
18 Answers
18
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Restoring MySQL database from physical files
Is it possible to restore a MySQL database from the physical database files. I have a directory that has the following file types:
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Can't connect to MySQL server error 111 [closed]
I installed mysql server on linux box IP = 192.168.1.100 but when i try to connect to this IP it alway error(111). but use localhost and 127.0.0.1 is OK.
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How to test which port MySQL is running on and whether it can be connected to?
I have installed MySQL and even logged in there as a user.
13 Answers
13
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实战做项目如何选择开源许可协议（一）-了解协议 - 开源 & Github - 清泛网...
实战做项目如何选择开源许可协议（一）-了解协议opensource_permission目前国内开源项目正在逐渐升温，中国也开始有不少优秀的开源项目突显出来。在大家摩拳擦掌准备加入开源大军时，也要知道这个圈子里的规则。...目前国内...