the value for
       the first <parameter>dbname</parameter> key word is checked to see
       if it is a <firstterm>connection string</firstterm>.  If so, it
       is <quote>expanded</quote> into the individual connection
       parameters extracted from the string.  The value is considered to
       be a connection string, rather than just a database name, if it
       contains an equal sign (<literal>=</literal>) or it begins with a
       URI scheme designator.  (More details on connection string formats
       appear in <xref linkend="libpq-connstring"/>.)  Only the first
       occurrence of <parameter>dbname</parameter> is treated in this way;
       any subsequent <parameter>dbname</parameter> parameter is processed
       as a plain database name.
      </para>

      <para>
       In general the parameter arrays are processed from start to end.
       If any key word is repeated, the last value (that is
       not <symbol>NULL</symbol> or empty) is used.  This rule applies in
       particular when a key word found in a connection string conflicts
       with one appearing in the <literal>keywords</literal> array.  Thus,
       the programmer may determine whether array entries can override or
       be overridden by values taken from a connection string.  Array
       entries appearing before an expanded <parameter>dbname</parameter>
       entry can be overridden by fields of the connection string, and in
       turn those fields are overridden by array entries appearing
       after <parameter>dbname</parameter> (but, again, only if those
       entries supply non-empty values).
      </para>

      <para>
       After processing all the array entries and any expanded connection
       string, any connection parameters that remain unset are filled with
       default values.  If an unset parameter's corresponding environment
       variable (see <xref linkend="libpq-envars"/>) is set, its value is
       used.  If the environment variable is not set either, then the
       parameter's built-in default value is used.
      </para>

     </listitem>
    </varlistentry>

    <varlistentry id="libpq-PQconnectdb">
     <term><function>PQconnectdb</function><indexterm><primary>PQconnectdb</primary></indexterm></term>
     <listitem>
      <para>
       Makes a new connection to the database server.

<synopsis>
PGconn *PQconnectdb(const char *conninfo);
</synopsis>
      </para>

      <para>
       This function opens a new database connection using the parameters taken
       from the string <literal>conninfo</literal>.
      </para>

      <para>
       The passed string can be empty to use all default parameters, or it can
       contain one or more parameter settings separated by whitespace,
       or it can contain a <acronym>URI</acronym>.
       See <xref linkend="libpq-connstring"/> for details.
     </para>


    </listitem>
    </varlistentry>

    <varlistentry id="libpq-PQsetdbLogin">
     <term><function>PQsetdbLogin</function><indexterm><primary>PQsetdbLogin</primary></indexterm></term>
     <listitem>
      <para>
       Makes a new connection to the database server.
<synopsis>
PGconn *PQsetdbLogin(const char *pghost,
                     const char *pgport,
                     const char *pgoptions,
                     const char *pgtty,
                     const char *dbName,
                     const char *login,
                     const char *pwd);
</synopsis>
       </para>

       <para>
        This is the predecessor of <xref linkend="libpq-PQconnectdb"/> with a fixed
        set of parameters.  It has the same functionality except that the
        missing parameters will always take on default values.  Write <symbol>NULL</symbol> or an
        empty string for any one of the fixed parameters that is to be defaulted.
      </para>

      <para>
        If the <parameter>dbName</parameter> contains
        an <symbol>=</symbol> sign or has a valid connection <acronym>URI</acronym> prefix, it