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_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/passworduser_name IDENTIFIED BY passworduser_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.
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.
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