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.