PostgreSQL

CONNECT
Prev	Up	36.14. Embedded SQL Commands	Home	Next

CONNECT

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

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. +

[ `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

`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.

Examples

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;

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

Prev	Up	Next
ALLOCATE DESCRIPTOR	Home	DEALLOCATE DESCRIPTOR

Submit correction

If you see anything in the documentation that is not correct, does not match your experience with the particular feature or requires further clarification, please use this form to report a documentation issue.