## Name

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 Postgres Pro 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_object`

  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 version() INTO :ver;
        EXEC SQL DISCONNECT;

        printf("version: %s\n", ver);

        EXEC SQL CONNECT TO :connection USER :user;
        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.

## See Also

DISCONNECT, SET CONNECTION