diff --git a/pkg/sql/opt/memo/statistics_builder.go b/pkg/sql/opt/memo/statistics_builder.go
index db3406b0f243..a1d965b25708 100644
--- a/pkg/sql/opt/memo/statistics_builder.go
+++ b/pkg/sql/opt/memo/statistics_builder.go
@@ -2726,14 +2726,6 @@ func max(a, b float64) float64 {
 	return b
 }
 
-// fraction returns a/b if a is less than b. Otherwise returns 1.
-func fraction(a, b float64) float64 {
-	if a < b {
-		return a / b
-	}
-	return 1
-}
-
 //////////////////////////////////////////////////
 // Helper functions for selectivity calculation //
 //////////////////////////////////////////////////
@@ -3624,8 +3616,8 @@ func (sb *statisticsBuilder) selectivityFromDistinctCount(
 	}
 
 	// Calculate the selectivity of the predicate.
-	nonNullSelectivity := props.MakeSelectivity(fraction(newDistinct, oldDistinct))
-	nullSelectivity := props.MakeSelectivity(fraction(colStat.NullCount, inputColStat.NullCount))
+	nonNullSelectivity := props.MakeSelectivityFromFraction(newDistinct, oldDistinct)
+	nullSelectivity := props.MakeSelectivityFromFraction(colStat.NullCount, inputColStat.NullCount)
 	return sb.predicateSelectivity(
 		nonNullSelectivity, nullSelectivity, inputColStat.NullCount, inputRowCount,
 	)
@@ -3658,8 +3650,8 @@ func (sb *statisticsBuilder) selectivityFromHistograms(
 		oldCount := oldHist.ValuesCount()
 
 		// Calculate the selectivity of the predicate.
-		nonNullSelectivity := props.MakeSelectivity(fraction(newCount, oldCount))
-		nullSelectivity := props.MakeSelectivity(fraction(colStat.NullCount, inputColStat.NullCount))
+		nonNullSelectivity := props.MakeSelectivityFromFraction(newCount, oldCount)
+		nullSelectivity := props.MakeSelectivityFromFraction(colStat.NullCount, inputColStat.NullCount)
 		selectivity.Multiply(sb.predicateSelectivity(
 			nonNullSelectivity, nullSelectivity, inputColStat.NullCount, inputStats.RowCount,
 		))
@@ -3749,7 +3741,7 @@ func (sb *statisticsBuilder) selectivityFromEquivalency(
 
 	// The selectivity of an equality condition var1=var2 is
 	// 1/max(distinct(var1), distinct(var2)).
-	return props.MakeSelectivity(fraction(1, maxDistinctCount))
+	return props.MakeSelectivityFromFraction(1, maxDistinctCount)
 }
 
 // selectivityFromEquivalenciesSemiJoin determines the selectivity of equality
@@ -3800,7 +3792,7 @@ func (sb *statisticsBuilder) selectivityFromEquivalencySemiJoin(
 		maxDistinctCountLeft = s.RowCount
 	}
 
-	return props.MakeSelectivity(fraction(minDistinctCountRight, maxDistinctCountLeft))
+	return props.MakeSelectivityFromFraction(minDistinctCountRight, maxDistinctCountLeft)
 }
 
 func (sb *statisticsBuilder) selectivityFromInvertedJoinCondition(
diff --git a/pkg/sql/opt/props/selectivity.go b/pkg/sql/opt/props/selectivity.go
index 5046485c454d..0ae630d4159b 100644
--- a/pkg/sql/opt/props/selectivity.go
+++ b/pkg/sql/opt/props/selectivity.go
@@ -34,6 +34,15 @@ func MakeSelectivity(sel float64) Selectivity {
 	return Selectivity{selectivityInRange(sel)}
 }
 
+// MakeSelectivityFromFraction calculates selectivity as a fraction of a and b
+// if a is less than b and returns OneSelectivity otherwise..
+func MakeSelectivityFromFraction(a, b float64) Selectivity {
+	if a < b {
+		return MakeSelectivity(a / b)
+	}
+	return OneSelectivity
+}
+
 // AsFloat returns the private selectivity field, allowing it to be accessed
 // outside of this package.
 func (s *Selectivity) AsFloat() float64 {
diff --git a/pkg/sql/opt/props/selectivity_test.go b/pkg/sql/opt/props/selectivity_test.go
index 3e0b9b183ae7..dde5889eb705 100644
--- a/pkg/sql/opt/props/selectivity_test.go
+++ b/pkg/sql/opt/props/selectivity_test.go
@@ -59,6 +59,13 @@ func TestSelectivity(t *testing.T) {
 	}
 	inf := math.MaxFloat64
 
+	// MakeSelectivityFromFraction variations.
+	test(MakeSelectivityFromFraction(1, 2), s(0.5))
+	test(MakeSelectivityFromFraction(1, 1), OneSelectivity)
+	test(MakeSelectivityFromFraction(1.5, 1), OneSelectivity)
+	test(MakeSelectivityFromFraction(1, 0), OneSelectivity)
+	test(MakeSelectivityFromFraction(0, 0), OneSelectivity)
+
 	// MinSelectivity variations.
 	test(MinSelectivity(s(0.4), s(0.5)), s(0.4))
 	test(MinSelectivity(s(0.5), s(0.4)), s(0.4))