## 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.

## See Also

[DISCONNECT](ecpg-sql-disconnect.html), [SET CONNECTION](ecpg-sql-set-connection.html)

