//函数原型描述
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const char *passwd, const char *db, unsigned int port, const char *unix_socket,
unsigned long client_flag)
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running on host. mysql_real_connect() must complete successfully before you can
execute any other API functions that require a valid MYSQL connection handle structure.
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calling mysql_real_connect() you must call mysql_init() to initialize the MYSQL
structure. You can change a lot of connect options with the mysql_options() call.
See Section 17.2.3.47, “mysql_options()”.
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string "localhost", a connection to the local host is assumed. If the OS supports sockets
(Unix) or named pipes (Windows), they are used instead of TCP/IP to connect to the server.
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string "", the current user is assumed. Under Unix, this is the current login name. Under
Windows ODBC, the current username must be specified explicitly. See Section 18.1.9.2,
“Configuring a MyODBC DSN on Windows”.
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in the user table for the user that have a blank (empty) password field are checked for a
match. This allows the database administrator to set up the MySQL privilege system in
such a way that users get different privileges depending on whether they have specified
a password.
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password encryption is handled automatically by the client API.
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to this value.
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that the host parameter determines the type of the connection.
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be used. Note that the host parameter determines the type of the connection.
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flags to enable certain features:
//上面描述了五个参数的主要取值,MYSQL *为mysql_init函数返回的指针,host为null或 // localhost时链接的是本地的计算机,当mysql默认安装在unix(或类unix)系统中,root账户是没// 有密码的,因此用户名使用root,密码为null,当db为空的时候,函数链接到默认数据库,在进行 // mysql安装时会存在默认的test数据库,因此此处可以使用test数据库名称,port端口为0,使用 // unix连接方式,unix_socket为null时,表明不使用socket或管道机制,最后一个参数经常设置为0
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changed rows.
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reserved words.
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seconds) of inactivity before closing the connection. The client's session wait_timeout
variable is set to the value of the session interactive_timeout variable.
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statements in a single string (separated by ‘;’). If this flag is not set,
multiple-statement execution is disabled. Added in MySQL 4.1.
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sets from multiple-statement executions or stored procedures. This is automatically
set if CLIENT_MULTI_STATEMENTS is set. Added in MySQL 4.1.
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ODBC. It causes the parser to generate an error if you use that syntax, which is useful
for trapping bugs in some ODBC programs.
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ODBC-friendly.
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application programs; it is set internally in the client library. Instead, use
mysql_ssl_set() before calling mysql_real_connect().
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than from an explicit value in the mysql_real_connect() call. To do this, call
mysql_options() with the MYSQL_READ_DEFAULT_FILE or MYSQL_READ_DEFAULT_GROUP option
before calling mysql_real_connect(). Then, in the mysql_real_connect() call, specify
the “no-value” value for each parameter to be read from an option file:
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the mysql_real_connect() call cannot be overridden in an option file, because the empty
string indicates explicitly that the MySQL account must have an empty password.)
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indicated in the descriptions given earlier in this section.
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was unsuccessful. For a successful connection, the return value is the same as the value
of the first parameter.
// 返回值:当连接成功时,返回MYSQL连接句柄,失败,返回NULL。当成功时,返回值与第一个参数值是// 相同的。
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library that uses a different protocol version. This can happen if you use a very old
client library to connect to a new server that wasn't started with the --old-protocol
option.
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the server or if the server died while executing the init-command.
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mysql_real_connect(mysql,"localhost","root",NULL,"test",0,NULL,0);
判断是否出错,出错调用mysql_error()
函数显示出错信息,或使用mysql_errno()函数获取出错代号。