CONNECT — establish a database connection
CONNECT TOconnection_target[ ASconnection_name] [ USERconnection_user] CONNECT TO DEFAULT CONNECTconnection_userDATABASEconnection_target
     The CONNECT command establishes a connection
     between the client and the PostgreSQL server.
    
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
containing a value in one of the above forms
            host variable of type char[]
            or VARCHAR[] containing a value in one of the
            above forms
           
connection_nameAn 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_userThe user name for the database connection.
        This parameter can also specify user name and password, using one the forms
        user_name/passworduser_name IDENTIFIED BY passworduser_name USING password
User name and password can be SQL identifiers, string constants, or host variables.
DEFAULTUse all default connection parameters, as defined by libpq.
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;
}
     CONNECT is specified in the SQL standard, but
     the format of the connection parameters is
     implementation-specific.