Postgresql 中文操作指南

CONNECT

CONNECT — 建立数据库连接

CONNECT — establish a database connection

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。

The CONNECT command establishes a connection between the client and the PostgreSQL server.

Parameters

connection_target #
- connection_target specifies the target server of the connection on one of several forms.
connection_name #
- An optional identifier for the connection, so that it can be referred to in other commands. This can be an SQL identifier or a host variable.
connection_user #
- The user name for the database connection.
- This parameter can also specify user name and password, using one the forms user_name_/password, user_name IDENTIFIED BY password, or user_name USING _password.
- User name and password can be SQL identifiers, string constants, or host variables.
DEFAULT #
- Use all default connection parameters, as defined by libpq.
[ 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 #
- containing a value in one of the above forms
host variable #
- host variable of type char[] or VARCHAR[] containing a value in one of the above forms

Examples

以下为用于指定连接参数的几种变体：

Here a several variants for specifying connection parameters:

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：

Here is an example program that illustrates the use of host variables to specify connection parameters:

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。

CONNECT is specified in the SQL standard, but the format of the connection parameters is implementation-specific.