diff --git a/src/jrd/Optimizer.cpp b/src/jrd/Optimizer.cpp
index 99530fdb55..6a9527b04a 100644
--- a/src/jrd/Optimizer.cpp
+++ b/src/jrd/Optimizer.cpp
@@ -3462,24 +3462,29 @@ bool OptimizerInnerJoin::cheaperRelationship(IndexRelationship* checkRelationshi
  *	is cheaper as withRelationship.
  *
  **************************************/
-	if (checkRelationship->cost == 0) {
+	if (checkRelationship->cost == 0)
 		return true;
-	}
-	if (withRelationship->cost == 0) {
+
+	if (withRelationship->cost == 0)
 		return false;
-	}
 
 	const double compareValue = checkRelationship->cost / withRelationship->cost;
 	if (compareValue >= 0.98 && compareValue <= 1.02)
 	{
-		// cost is nearly the same, now check on cardinality
-		if (checkRelationship->cardinality < withRelationship->cardinality) {
-			return true;
+		// cost is nearly the same, now check uniqueness and cardinality
+
+		if (checkRelationship->unique == withRelationship->unique)
+		{
+			if (checkRelationship->cardinality < withRelationship->cardinality)
+				return true;
 		}
+		else if (checkRelationship->unique)
+			return true;
+		else if (withRelationship->unique)
+			return false;
 	}
-	else if (checkRelationship->cost < withRelationship->cost) {
+	else if (checkRelationship->cost < withRelationship->cost)
 		return true;
-	}
 
 	return false;
 }
@@ -3786,20 +3791,22 @@ void OptimizerInnerJoin::getIndexedRelationship(InnerJoinStreamInfo* baseStream,
 		indexRelationship->stream = testStream->stream;
 		indexRelationship->unique = candidate->unique;
 		indexRelationship->cost = candidate->cost;
-		indexRelationship->cardinality = csb_tail->csb_cardinality * candidate->selectivity;
+		indexRelationship->cardinality = candidate->unique ?
+			csb_tail->csb_cardinality : csb_tail->csb_cardinality * candidate->selectivity;
 
 		// indexRelationship are kept sorted on cost and unique in the indexRelations array.
-		// The unique and cheapest indexed relatioships are on the first position.
+		// The unique and cheapest indexed relationships are on the first position.
 		size_t index = 0;
 		for (; index < baseStream->indexedRelationships.getCount(); index++)
 		{
-			if (cheaperRelationship(indexRelationship, baseStream->indexedRelationships[index])) {
+			if (cheaperRelationship(indexRelationship, baseStream->indexedRelationships[index]))
 				break;
-			}
 		}
+
 		baseStream->indexedRelationships.insert(index, indexRelationship);
 		testStream->previousExpectedStreams++;
 	}
+
 	delete candidate;
 	delete optimizerRetrieval;