CONNECT

CONNECT-构建数据库连接

Synopsis

CONNECT TO connection_target [ AS connection_name ] [ USER connection_user ]
CONNECT TO DEFAULT
CONNECT connection_user
DATABASE connection_target

Description

CONNECT命令在 Client 端和 PostgreSQL 服务器之间构建连接。

Parameters

• connection_target

  • • connection_target *以几种形式之一指定连接的目标服务器。

• [ database_name ] [ @ host ] [ : port ]

  • 通过 TCP/IP 连接

  • unix:postgresql:// host [ : port ] / [ database_name ] [ ? connection_option ]

    • 通过 Unix 域套接字连接

  • tcp:postgresql:// host [ : port ] / [ database_name ] [ ? connection_option ]

    • 通过 TCP/IP 连接

  • SQL 字符串常量

    • 包含上述形式之一的值

  • host variable

    • 类型char[]或VARCHAR[]的主机变量，其中包含上述形式之一的值

• connection_name

  • 连接的可选标识符，以便可以在其他命令中引用它。这可以是 SQL 标识符或主机变量。

• connection_user

  • 数据库连接的用户名。

此参数还可以使用user_name/password，user_name IDENTIFIED BY password或user_name USING password形式指定用户名和密码。

用户名和密码可以是 SQL 标识符，字符串常量或主机变量。

• DEFAULT

  • 使用 libpq 定义的所有默认连接参数。

Examples

这里是用于指定连接参数的几种变体：

EXEC SQL CONNECT TO "connectdb" AS main;
EXEC SQL CONNECT TO "connectdb" AS second;
EXEC SQL CONNECT TO "unix:postgresql://200.46.204.71/connectdb" AS main USER connectuser;
EXEC SQL CONNECT TO "unix:postgresql://localhost/connectdb" AS main USER connectuser;
EXEC SQL CONNECT TO 'connectdb' AS main;
EXEC SQL CONNECT TO 'unix:postgresql://localhost/connectdb' AS main USER :user;
EXEC SQL CONNECT TO :db AS :id;
EXEC SQL CONNECT TO :db USER connectuser USING :pw;
EXEC SQL CONNECT TO @localhost AS main USER connectdb;
EXEC SQL CONNECT TO REGRESSDB1 as main;
EXEC SQL CONNECT TO AS main USER connectdb;
EXEC SQL CONNECT TO connectdb AS :id;
EXEC SQL CONNECT TO connectdb AS main USER connectuser/connectdb;
EXEC SQL CONNECT TO connectdb AS main;
EXEC SQL CONNECT TO connectdb@localhost AS main;
EXEC SQL CONNECT TO tcp:postgresql://localhost/ USER connectdb;
EXEC SQL CONNECT TO tcp:postgresql://localhost/connectdb USER connectuser IDENTIFIED BY connectpw;
EXEC SQL CONNECT TO tcp:postgresql://localhost:20/connectdb USER connectuser IDENTIFIED BY connectpw;
EXEC SQL CONNECT TO unix:postgresql://localhost/ AS main USER connectdb;
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb AS main USER connectuser;
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb USER connectuser IDENTIFIED BY "connectpw";
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb USER connectuser USING "connectpw";
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb?connect_timeout=14 USER connectuser;

这是一个示例程序，说明了如何使用主机变量指定连接参数：

int
main(void)
{
EXEC SQL BEGIN DECLARE SECTION;
    char *dbname     = "testdb";    /* database name */
    char *user       = "testuser";  /* connection user name */
    char *connection = "tcp:postgresql://localhost:5432/testdb";
                                    /* connection string */
    char ver[256];                  /* buffer to store the version string */
EXEC SQL END DECLARE SECTION;

    ECPGdebug(1, stderr);

    EXEC SQL CONNECT TO :dbname USER :user;
    EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT;
    EXEC SQL SELECT version() INTO :ver;
    EXEC SQL DISCONNECT;

    printf("version: %s\n", ver);

    EXEC SQL CONNECT TO :connection USER :user;
    EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT;
    EXEC SQL SELECT version() INTO :ver;
    EXEC SQL DISCONNECT;

    printf("version: %s\n", ver);

    return 0;
}

Compatibility

CONNECT在 SQL 标准中指定，但是连接参数的格式是特定于实现的。

See Also

DISCONNECT, SET CONNECTION