</para>

  <para>
   Here are some examples of <command>CONNECT</command> statements:
<programlisting>
EXEC SQL CONNECT TO mydb@sql.mydomain.com;

EXEC SQL CONNECT TO tcp:postgresql://sql.mydomain.com/mydb AS myconnection USER john;

EXEC SQL BEGIN DECLARE SECTION;
const char *target = "mydb@sql.mydomain.com";
const char *user = "john";
const char *passwd = "secret";
EXEC SQL END DECLARE SECTION;
 ...
EXEC SQL CONNECT TO :target USER :user USING :passwd;
/* or EXEC SQL CONNECT TO :target USER :user/:passwd; */
</programlisting>
   The last example makes use of the feature referred to above as
   character variable references.  You will see in later sections how C
   variables can be used in SQL statements when you prefix them with a
   colon.
  </para>

  <para>
   Be advised that the format of the connection target is not
   specified in the SQL standard.  So if you want to develop portable
   applications, you might want to use something based on the last
   example above to encapsulate the connection target string
   somewhere.
  </para>

  <para>
   If untrusted users have access to a database that has not adopted a
   <link linkend="ddl-schemas-patterns">secure schema usage pattern</link>,
   begin each session by removing publicly-writable schemas
   from <varname>search_path</varname>.  For example,
   add <literal>options=-c search_path=</literal>
   to <literal><replaceable>options</replaceable></literal>, or
   issue <literal>EXEC SQL SELECT pg_catalog.set_config('search_path', '',
   false);</literal> after connecting.  This consideration is not specific to
   ECPG; it applies to every interface for executing arbitrary SQL commands.
  </para>
  </sect2>

  <sect2 id="ecpg-set-connection">
   <title>Choosing a Connection</title>

  <para>
   SQL statements in embedded SQL programs are by default executed on
   the current connection, that is, the most recently opened one.  If
   an application needs to manage multiple connections, then there are
   three ways to handle this.
  </para>

  <para>
   The first option is to explicitly choose a connection for each SQL
   statement, for example:
<programlisting>
EXEC SQL AT <replaceable>connection-name</replaceable> SELECT ...;
</programlisting>
   This option is particularly suitable if the application needs to
   use several connections in mixed order.
  </para>

  <para>
   If your application uses multiple threads of execution, they cannot share a
   connection concurrently. You must either explicitly control access to the connection
   (using mutexes) or use a connection for each thread.
  </para>

  <para>
   The second option is to execute a statement to switch the current
   connection.  That statement is:
<programlisting>
EXEC SQL SET CONNECTION <replaceable>connection-name</replaceable>;
</programlisting>
   This option is particularly convenient if many statements are to be
   executed on the same connection.
  </para>

  <para>
   Here is an example program managing multiple database connections:
<programlisting><![CDATA[
#include <stdio.h>

EXEC SQL BEGIN DECLARE SECTION;
    char dbname[1024];
EXEC SQL END DECLARE SECTION;

int
main()
{
    EXEC SQL CONNECT TO testdb1 AS con1 USER testuser;
    EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT;
    EXEC SQL CONNECT TO testdb2 AS con2 USER testuser;
    EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT;
    EXEC SQL CONNECT TO testdb3 AS con3 USER testuser;
    EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT;

    /* This query would be executed in the last opened database "testdb3". */
    EXEC SQL SELECT current_database() INTO :dbname;
    printf("current=%s (should be testdb3)\n", dbname);

    /* Using "AT" to run a query in "testdb2" */
    EXEC SQL AT con2 SELECT current_database() INTO :dbname;
    printf("current=%s (should be testdb2)\n", dbname);

    /* Switch the current connection to "testdb1". */
    EXEC