MySql连接字符串

The port 3306 is the default MySql port.

The value is ignored if Unix socket is used.

Use this to connect to a server in a replicated server configuration without concern on which server to use.

Use SSL if the server supports it, but allow connection in all cases

This option is available from Connector/NET version 6.2.1

Always use SSL. Deny connection if server does not support SSL.

This option is available from Connector/NET version 6.2.1

This option is available from Connector/NET version 6.2.1

This option is available from Connector/NET version 6.2.1

This option is available from Connector/NET version 6.2.1

This option is available from Connector/NET version 5.2.2

Returns a MySqlDateTime object for invalid values and a System.DateTime object for valid values

Returns System.DateTime.MinValue valued System.DateTime object for invalid values and a System.DateTime object for valid values.

The use of auto enlist transactionscope (default behaviour) could cause trouble in medium trust environments.

Default behaviour is that parameters for stored routines (stored procedures) are checked against the server

Some permissions and value casting related errors reported fixed when using this connection option.

The default behaviour is to read tables mysql.proc/INFORMATION_SCHEMA.ROUTINES and try to map provided command parameter values to the called procedures parameters and type cast values accordingly.

This can be troublesome if permissions to the (aforementioned) sproc info tables are insufficient.

The driver will not automatically map the parameters so you must manually set parameter types and you must also make sure to add the parameters to the command object in the exact order as appeared in the procedure definition.

This option is available from Connector/NET version 5.0.4

Specifying DefaultTableCacheAge is optional, default value is 60 seconds.

This option is available from Connector/NET version 6.4

This option is available from Connector/NET version 5.2.6

From version 6.2 idle connections are removed from the pool, freeing resources on the client (sockets) and the server (sockets and threads). Do not manually keep (global) connections and open close. Keep connection object creation and disposal as tight as possible, this might be counterintuitive but pooling mechanisms will take care of caching well and your code will be cleaner.

This is the default behaviour.

Default values are 0 and 100.

Makes an additional round trip to the server when obtaining a connection from the pool and connection state will be reset.

This is useful in load balancing scenarios when available servers change you don't want 100 constant connections in the pool pointing to only one server.

Specified in seconds, the amount of time after connection object creation the connection will be destroyed. Destruction will only happen when connections are returned to pool.

A connection might be long lived in the pool, however the connections server settings are updated (SHOW VARIABLES command) each time returned to the pool. This makes the client use of the connection object up to date with the correct server settings. However this causes a round trip and to optimize pooling performance this behaviour can be turned off.

This option is available from Connector/NET version 6.3

This option is available from Connector/NET version 6.4.4

The Windows Native Authentication Plugin must be installed for this to work.

Number of seconds between each keep-alive package send.

This option is available from Connector/NET version 6.1.1

The default is 25, meaning that stored procedure meta data (such as input/output data types etc) for the latest 25 called procedures will be cached in client memory.

This option is available from Connector/NET version 5.0.2

This enables Visual Studio wizards that bracket symbols with [] to work with Connector/Net. This option incurs a performance hit, so should only be used if necessary.

This option is available from Connector/NET version 6.3.1

Use this one to specify a default command timeout for the connection. Please note that the property in the connection string does not supercede the individual command timeout property on an individual command object.

This option is available from Connector/NET version 5.1.4.

Use this one to specify the length in seconds to wait for a server connection before terminating the attempt and receive an error.

Use this one to instruct the provider to ignore any command prepare statements and prevent corruption issues with server side prepared statements.

The option was added in Connector/NET version 5.0.3 and Connector/NET version 1.0.9.

Use this one to specify which network protocol to use for the connection.

"socket" is the default value used if the key isn't specified. Value "tcp" is an equivalent for "socket".

Use "pipe" to use a named pipes connection, "unix" for a Unix socket connection and "memory" to use MySQL shared memory.

It's possible to explicit set the shared memory object name used for communication.

It's possible to explicit set the pipe name used for communication, if not set, 'mysql' is the default value.

It is the port value of -1 that tells the driver to use named pipes network protocol. This is available on Windows only. The value is ignored if Unix socket is used.

It's possible to explicit set the shared memory object name used for communication.

Use this one to specify which character set to use to encode queries sent to the server.

Note! Use lower case value utf8 and not upper case UTF8 as this will fail.

Note that resultsets still are returned in the character set of the data returned.

说明 : string1,string2代表字符串,concat函数在连接字符串的时候，只要其中一个是NULL,那么将返回NULL

结果：

说明：将多个字符串连接成一个字符串，但是可以一次性指定分隔符～（concat_ws就是concat with separator）

GROUP_CONCAT([DISTINCT] expr [,expr ...] [ORDER BY {unsigned_integer | col_name | expr} [ASC | DESC] [,col_name ...]] [SEPARATOR str_val])

说明：

DISTINCT：去除重复值

expr [,expr ...]：一个或多个字段（或表达式）

ORDER BY {unsigned_integer | col_name | expr} [ASC | DESC] [,col_name ...]：根据字段或表达式进行排序，可多个

SEPARATOR str_val：分隔符（默认为英文逗号）

group_concat()函数在处理大数据的时候，会发现内容被截取了

其实MYSQL内部对这个是有设置的，默认不设置的长度是1024，如果我们需要更大，就需要手工去修改配置文件

C#中连接MySql的字符串步骤如下：

1、打开Visual Studio 2015开发工具，新建一个Windows窗体应用程序。

2、在Mysql的官方网站上找到Mysql连接需要的DLL，下载后的DLL文件目录如下图。

3、接下来将所下载的DLL目录导入到项目的引用目录下面。

4、然后我们在项目的Form窗体中添加一个button按钮，下面将实现的是点击按钮进行MySql的连接。

5、打开Form1.cs文件，在顶部我们导入MySql.Data.MySqlClient命名空间，我们要使用的数据库连接方法都在这个命名空间里。

6、接下来在程序中准备一个连接字符串，字符串中需要指定数据库名称，用户名和密码。

7、然后实现按钮的点击方法，在方法中我们通过MySqlConnection进行连接，如下图所示，MySqlConnection需要传入连接字符串。

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