diff --git a/src/main/java/net/helenus/core/HelenusSession.java b/src/main/java/net/helenus/core/HelenusSession.java
index aeee3c8..c4324c0 100644
--- a/src/main/java/net/helenus/core/HelenusSession.java
+++ b/src/main/java/net/helenus/core/HelenusSession.java
@@ -235,7 +235,7 @@ public class HelenusSession extends AbstractSessionOperations implements Closeab
             }
           } else {
             value = valueMap.get(prop.getPropertyName());
-            binder.setValueForProperty(prop, value.toString());
+            if (value != null) binder.setValueForProperty(prop, value.toString());
           }
         }
         if (binder.isBound()) {
diff --git a/src/main/java/net/helenus/core/SchemaUtil.java b/src/main/java/net/helenus/core/SchemaUtil.java
index 721e512..0a12d35 100644
--- a/src/main/java/net/helenus/core/SchemaUtil.java
+++ b/src/main/java/net/helenus/core/SchemaUtil.java
@@ -165,6 +165,14 @@ public final class SchemaUtil {
       }
     }
 
+    if (p.size() == 0 && c.size() == 0)
+      return "{"
+          + properties
+              .stream()
+              .map(HelenusProperty::getPropertyName)
+              .collect(Collectors.joining(", "))
+          + "}";
+
     return "("
         + ((p.size() > 1) ? "(" + String.join(", ", p) + ")" : p.get(0))
         + ((c.size() > 0)
diff --git a/src/main/java/net/helenus/mapping/HelenusMappingEntity.java b/src/main/java/net/helenus/mapping/HelenusMappingEntity.java
index cf343bb..9e0a2cc 100644
--- a/src/main/java/net/helenus/mapping/HelenusMappingEntity.java
+++ b/src/main/java/net/helenus/mapping/HelenusMappingEntity.java
@@ -31,6 +31,7 @@ import net.helenus.mapping.annotation.*;
 import net.helenus.mapping.validator.DistinctValidator;
 import net.helenus.support.HelenusMappingException;
 import org.apache.commons.lang3.ClassUtils;
+import org.apache.commons.lang3.StringUtils;
 
 public final class HelenusMappingEntity implements HelenusEntity {
 
@@ -128,7 +129,24 @@ public final class HelenusMappingEntity implements HelenusEntity {
           for (ConstraintValidator<?, ?> constraint :
               MappingUtil.getValidators(prop.getGetterMethod())) {
             if (constraint.getClass().isAssignableFrom(DistinctValidator.class)) {
-              UnboundFacet facet = new UnboundFacet(prop);
+              DistinctValidator validator = (DistinctValidator) constraint;
+              String[] values = validator.value();
+              UnboundFacet facet;
+              if (values != null && values.length >= 1 && !(StringUtils.isBlank(values[0]))) {
+                List<HelenusProperty> props = new ArrayList<HelenusProperty>(values.length + 1);
+                props.add(prop);
+                for (String value : values) {
+                  for (HelenusProperty p : orderedProps) {
+                    String name = p.getPropertyName();
+                    if (name.equals(value) && !name.equals(prop.getPropertyName())) {
+                      props.add(p);
+                    }
+                  }
+                }
+                facet = new UnboundFacet(props);
+              } else {
+                facet = new UnboundFacet(prop);
+              }
               facetsBuilder.add(facet);
               break;
             }
diff --git a/src/main/java/net/helenus/mapping/annotation/Constraints.java b/src/main/java/net/helenus/mapping/annotation/Constraints.java
index d1b99d2..22ffbdc 100644
--- a/src/main/java/net/helenus/mapping/annotation/Constraints.java
+++ b/src/main/java/net/helenus/mapping/annotation/Constraints.java
@@ -228,10 +228,11 @@ public final class Constraints {
   public @interface Distinct {
 
     /**
-     * User defined Enum to further restrict the items in the set.
+     * User defined list of properties that combine with this one to result in a distinct
+     * combination in the table.
      *
      * @return Java
      */
-    Class<? extends Enum> value() default Enum.class;
+    String[] value() default "";
   }
 }
diff --git a/src/main/java/net/helenus/mapping/validator/DistinctValidator.java b/src/main/java/net/helenus/mapping/validator/DistinctValidator.java
index 8dc4711..40c30d7 100644
--- a/src/main/java/net/helenus/mapping/validator/DistinctValidator.java
+++ b/src/main/java/net/helenus/mapping/validator/DistinctValidator.java
@@ -22,13 +22,20 @@ import net.helenus.mapping.annotation.Constraints;
 public final class DistinctValidator
     implements ConstraintValidator<Constraints.Distinct, CharSequence> {
 
+  private Constraints.Distinct annotation;
+
   @Override
-  public void initialize(Constraints.Distinct constraintAnnotation) {}
+  public void initialize(Constraints.Distinct constraintAnnotation) {
+    annotation = constraintAnnotation;
+  }
 
   @Override
   public boolean isValid(CharSequence value, ConstraintValidatorContext context) {
-    // TODO(gburd): if there is an Enum type supplied, check that value is valid
-    // Enum.name()
+    // TODO(gburd): check that the list contains valid property names.
     return true;
   }
+
+  public String[] value() {
+    return annotation == null ? null : annotation.value();
+  }
 }
diff --git a/src/test/java/net/helenus/test/integration/core/unitofwork/UnitOfWorkTest.java b/src/test/java/net/helenus/test/integration/core/unitofwork/UnitOfWorkTest.java
index 1b5e01f..1c535c1 100644
--- a/src/test/java/net/helenus/test/integration/core/unitofwork/UnitOfWorkTest.java
+++ b/src/test/java/net/helenus/test/integration/core/unitofwork/UnitOfWorkTest.java
@@ -41,8 +41,13 @@ interface Widget {
   UUID id();
 
   @Index
-  @Constraints.Distinct()
+  @Constraints.Distinct
   String name();
+
+  @Constraints.Distinct(value = {"b"})
+  String a();
+
+  String b();
 }
 
 public class UnitOfWorkTest extends AbstractEmbeddedCassandraTest {
@@ -74,6 +79,8 @@ public class UnitOfWorkTest extends AbstractEmbeddedCassandraTest {
             .<Widget>insert(widget)
             .value(widget::id, key)
             .value(widget::name, RandomString.make(20))
+            .value(widget::a, RandomString.make(10))
+            .value(widget::b, RandomString.make(10))
             .sync();
 
     try (UnitOfWork uow = session.begin()) {
@@ -118,6 +125,8 @@ public class UnitOfWorkTest extends AbstractEmbeddedCassandraTest {
               .<Widget>insert(widget)
               .value(widget::id, key1)
               .value(widget::name, RandomString.make(20))
+              .value(widget::a, RandomString.make(10))
+              .value(widget::b, RandomString.make(10))
               .sync(uow1);
 
       try (UnitOfWork uow2 = session.begin(uow1)) {
@@ -138,6 +147,8 @@ public class UnitOfWorkTest extends AbstractEmbeddedCassandraTest {
                 .<Widget>insert(widget)
                 .value(widget::id, key2)
                 .value(widget::name, RandomString.make(20))
+                .value(widget::a, RandomString.make(10))
+                .value(widget::b, RandomString.make(10))
                 .sync(uow2);
 
         uow2.commit()
@@ -151,7 +162,8 @@ public class UnitOfWorkTest extends AbstractEmbeddedCassandraTest {
       w4 =
           session
               .<Widget>select(widget)
-              .where(widget::id, eq(key2))
+              .where(widget::a, eq(w3.a()))
+              .and(widget::b, eq(w3.b()))
               .single()
               .sync(uow1)
               .orElse(null);
@@ -175,6 +187,8 @@ public class UnitOfWorkTest extends AbstractEmbeddedCassandraTest {
           .<Widget>insert(widget)
           .value(widget::id, key)
           .value(widget::name, RandomString.make(20))
+          .value(widget::a, RandomString.make(10))
+          .value(widget::b, RandomString.make(10))
           .sync(uow);
 
       // This should read from the database and return a Widget.
@@ -209,6 +223,8 @@ public class UnitOfWorkTest extends AbstractEmbeddedCassandraTest {
             .<Widget>insert(widget)
             .value(widget::id, key)
             .value(widget::name, RandomString.make(20))
+            .value(widget::a, RandomString.make(10))
+            .value(widget::b, RandomString.make(10))
             .sync();
 
     try (UnitOfWork uow = session.begin()) {
@@ -271,6 +287,8 @@ public class UnitOfWorkTest extends AbstractEmbeddedCassandraTest {
             .<Widget>insert(widget)
             .value(widget::id, key)
             .value(widget::name, RandomString.make(20))
+            .value(widget::a, RandomString.make(10))
+            .value(widget::b, RandomString.make(10))
             .sync();
 
     try (UnitOfWork uow = session.begin()) {