Postgresql 中文操作指南

CONNECT

CONNECT — 建立数据库连接

Synopsis

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

Description

CONNECT 命令在客户端和 PostgreSQL 服务器之间建立连接。

Parameters

  • connection_target #

    • connection_target 在多种形式中指定连接的目标服务器。

  • connection_name #

    • 连接的可选标识符，以便在其他命令中引用它。这可以是 SQL 标识符或宿主变量。

  • connection_user #

    • 数据库连接的用户名。

    • 此参数也可以使用 user_name/password 、 user_name IDENTIFIED BY password 或 user_name USING password 之一的形式指定用户名和密码。

    • 用户名和密码可以是 SQL 标识符、字符串常量或宿主变量。

  • DEFAULT #

    • 使用由 libpq 定义的所有默认连接参数。

  • [ database_name ] [ @_host ] [ :_port ] #

    • Connect over TCP/IP

  • unix:postgresql://_host [ :_port ] / [ database_name ] [ ?__connection_option ] #

    • Connect over Unix-domain sockets

  • tcp:postgresql://_host [ :_port ] / [ database_name ] [ ?__connection_option ] #

    • Connect over TCP/IP

  • SQL string constant #

    • 包含上述其中一种形式的值

  • host variable #

    • 类型为 char[] 或 VARCHAR[] 的宿主变量，其中包含上述其中一种形式的值

Examples

以下为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;

以下示例程序说明了如何使用宿主变量指定连接参数：

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，但连接参数的格式与实现相关。

See Also

DISCONNECT ， SET CONNECTION