D.11.2 CONNECT

Name

CONNECT -- establish a database connection

Synopsis

CONNECT TO connection_target [ AS connection_name ] [ USER connection_user_name ]

CONNECT TO DEFAULT

CONNECT connection_user_name

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 fixed-length string (trailing spaces are ignored) 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_name

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(fixed-length string, trailing spaces are ignored).

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 END-EXEC.
EXEC SQL CONNECT TO "connectdb" AS second END-EXEC.
EXEC SQL CONNECT TO "unix:postgresql://localhost/connectdb" AS main USER connectuser END-EXEC.
EXEC SQL CONNECT TO 'connectdb' AS main END-EXEC.
EXEC SQL CONNECT TO 'unix:postgresql://localhost/connectdb' AS main USER :user END-EXEC.
EXEC SQL CONNECT TO :dbn AS :idt END-EXEC.
EXEC SQL CONNECT TO :dbn USER connectuser USING :pw END-EXEC.
EXEC SQL CONNECT TO @localhost AS main USER connectdb END-EXEC.
EXEC SQL CONNECT TO REGRESSDB1 as main END-EXEC.
EXEC SQL CONNECT TO connectdb AS :idt END-EXEC.
EXEC SQL CONNECT TO connectdb AS main USER connectuser/connectdb END-EXEC.
EXEC SQL CONNECT TO connectdb AS main END-EXEC.
EXEC SQL CONNECT TO connectdb@localhost AS main END-EXEC.
EXEC SQL CONNECT TO tcp:postgresql://localhost/ USER connectdb END-EXEC.
EXEC SQL CONNECT TO tcp:postgresql://localhost/connectdb USER connectuser IDENTIFIED BY connectpw END-EXEC.
EXEC SQL CONNECT TO tcp:postgresql://localhost:20/connectdb USER connectuser IDENTIFIED BY connectpw END-EXEC.
EXEC SQL CONNECT TO unix:postgresql://localhost/ AS main USER connectdb END-EXEC.
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb AS main USER connectuser END-EXEC.
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb USER connectuser IDENTIFIED BY "connectpw" END-EXEC.
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb USER connectuser USING "connectpw" END-EXEC.
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb?connect_timeout=14 USER connectuser END-EXEC.

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

EXEC SQL BEGIN DECLARE SECTION END-EXEC.
*   database name
    01 DBNAME PIC X(6).
*   connection user name
    01 USER PIC X(8).
*   connection string
    01 CONNECTION PIC X(38).

    01 VER PIC X(256).
EXEC SQL END DECLARE SECTION END-EXEC.

	MOVE "testdb" TO DBNAME.
	MOVE "testuser" TO USER.
	MOVE "tcp:postgresql://localhost:5432/testdb" TO CONNECTION.

    EXEC SQL CONNECT TO :DBNAME USER :USER END-EXEC.
    EXEC SQL SELECT version() INTO :VER END-EXEC.
    EXEC SQL DISCONNECT END-EXEC.


    DISPLAY "version: " VER.

    EXEC SQL CONNECT TO :CONNECTION USER :USER END-EXEC.
    EXEC SQL SELECT version() INTO :VER END-EXEC.
    EXEC SQL DISCONNECT END-EXEC.

    DISPLAY "version: " VER.

Compatibility

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