Doc: trivial wording adjustment.

tglsfdc · tglsfdc · commit c38cadc0907a · 2021-05-06T09:59:11.000-04:00
Improve self-referential foreign key example, per suggestion from David Johnston. Discussion: https://postgr.es/m/CAKFQuwZTke7+HUn4YUGqu2+gAPi4Cy18TXMrg_Z5nADkxfPNMw@mail.gmail.com
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
@@ -956,7 +956,7 @@ CREATE TABLE tree (
 );
 </programlisting>
     A top-level node would have NULL <structfield>parent_id</structfield>,
-    but non-NULL <structfield>parent_id</structfield> entries would be
+    while non-NULL <structfield>parent_id</structfield> entries would be
     constrained to reference valid rows of the table.
    </para>
 
