Clean up description of SET CONSTRAINTS.

doc/src/sgml/ref/set.sgml

 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.41 2000/04/14 23:12:29 momjian Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.42 2000/04/18 15:23:34 thomas Exp $
 Postgres documentation
 -->
 
@@ -266,12 +266,14 @@ SELECT setseed(<replaceable>value</replaceable>);
      </varlistentry>
 
      <varlistentry>
-      <term>CONSTRAINT</term>
+      <term>CONSTRAINTS</term>
       <listitem>
        <para>
-	SET CONSTRAINTS controls the frequency of foreign key
-	constratint checking in the current transaction. Allowed
-	parameters are:
+	SET CONSTRAINTS affects the behavior of constraint evaluation
+	in the current transaction.
+	SET CONSTRAINTS, specified
+	in SQL3, has these allowed parameters:
+
 	<variablelist>
 	 <varlistentry>
 	  <term><replaceable class="parameter">constraintlist</replaceable></term>
@@ -295,12 +297,19 @@ SELECT setseed(<replaceable>value</replaceable>);
        </para>
 
        <para>
-	In <option>DEFERRED</option> mode, foreign key constraints
-	marked as <option>DEFERRABLE</option> are checked only at
-	transaction commit.
 	In <option>IMMEDIATE</option> mode, foreign key constraints
 	are checked at the end of each query.
        </para>
+
+       <para>
+	In <option>DEFERRED</option> mode, foreign key constraints
+	marked as <option>DEFERRABLE</option> are checked only at
+	transaction commit or  until its mode is explicitly set to 
+	<option>IMMEDIATE</option>.
+	This is actually only done for foreign  key
+	constraints,  so  it  does  not  apply  to  UNIQUE  or  other
+	constraints.
+       </para>
       </listitem>
      </varlistentry>