diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/AliasAwareOutputExpression.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/AliasAwareOutputExpression.scala
index 4d9d69d14fe5f..cfe229945929c 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/AliasAwareOutputExpression.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/AliasAwareOutputExpression.scala
@@ -95,7 +95,7 @@ trait AliasAwareQueryOutputOrdering[T <: QueryPlan[T]]
   }
 
   override final def outputOrdering: Seq[SortOrder] = {
-    if (hasAlias) {
+    val newOrdering: Iterator[Option[SortOrder]] = if (hasAlias) {
       // Take the first `SortOrder`s only until they can be projected.
       // E.g. we have child ordering `Seq(SortOrder(a), SortOrder(b))` then
       // if only `a AS x` can be projected then we can return Seq(SortOrder(x))`
@@ -112,9 +112,21 @@ trait AliasAwareQueryOutputOrdering[T <: QueryPlan[T]]
         } else {
           None
         }
-      }.takeWhile(_.isDefined).flatten.toSeq
+      }
     } else {
-      orderingExpressions
+      // Make sure the returned ordering are valid (only reference output attributes of the current
+      // plan node). Same as above (the if branch), we take the first ordering expressions that are
+      // all valid.
+      val outputSet = AttributeSet(outputExpressions.map(_.toAttribute))
+      orderingExpressions.iterator.map { order =>
+        val validChildren = order.children.filter(_.references.subsetOf(outputSet))
+        if (validChildren.nonEmpty) {
+          Some(order.copy(child = validChildren.head, sameOrderExpressions = validChildren.tail))
+        } else {
+          None
+        }
+      }
     }
+    newOrdering.takeWhile(_.isDefined).flatten.toSeq
   }
 }
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/AliasAwareOutputExpression.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/AliasAwareOutputExpression.scala
index a09c719cf840d..e1dcab80af307 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/AliasAwareOutputExpression.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/AliasAwareOutputExpression.scala
@@ -18,7 +18,7 @@ package org.apache.spark.sql.execution
 
 import scala.collection.mutable
 
-import org.apache.spark.sql.catalyst.expressions.Expression
+import org.apache.spark.sql.catalyst.expressions.{AttributeSet, Expression}
 import org.apache.spark.sql.catalyst.plans.{AliasAwareOutputExpression, AliasAwareQueryOutputOrdering}
 import org.apache.spark.sql.catalyst.plans.physical.{Partitioning, PartitioningCollection, UnknownPartitioning}
 
@@ -29,7 +29,7 @@ import org.apache.spark.sql.catalyst.plans.physical.{Partitioning, PartitioningC
 trait PartitioningPreservingUnaryExecNode extends UnaryExecNode
   with AliasAwareOutputExpression {
   final override def outputPartitioning: Partitioning = {
-    if (hasAlias) {
+    val partitionings: Seq[Partitioning] = if (hasAlias) {
       flattenPartitioning(child.outputPartitioning).flatMap {
         case e: Expression =>
           // We need unique partitionings but if the input partitioning is
@@ -44,13 +44,19 @@ trait PartitioningPreservingUnaryExecNode extends UnaryExecNode
             .take(aliasCandidateLimit)
             .asInstanceOf[Stream[Partitioning]]
         case o => Seq(o)
-      } match {
-        case Seq() => UnknownPartitioning(child.outputPartitioning.numPartitions)
-        case Seq(p) => p
-        case ps => PartitioningCollection(ps)
       }
     } else {
-      child.outputPartitioning
+      // Filter valid partitiongs (only reference output attributes of the current plan node)
+      val outputSet = AttributeSet(outputExpressions.map(_.toAttribute))
+      flattenPartitioning(child.outputPartitioning).filter {
+        case e: Expression => e.references.subsetOf(outputSet)
+        case _ => true
+      }
+    }
+    partitionings match {
+      case Seq() => UnknownPartitioning(child.outputPartitioning.numPartitions)
+      case Seq(p) => p
+      case ps => PartitioningCollection(ps)
     }
   }
 
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/PlannerSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/PlannerSuite.scala
index e9cb77ec95c4d..4b3d3a4b8058a 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/PlannerSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/PlannerSuite.scala
@@ -1129,9 +1129,10 @@ class PlannerSuite extends SharedSparkSession with AdaptiveSparkPlanHelper {
         assert(sortNodes.size == 3)
         val outputOrdering = planned.outputOrdering
         assert(outputOrdering.size == 1)
-        // Sort order should have 3 childrens, not 4. This is because t1.id*2 and 2*t1.id are same
-        assert(outputOrdering.head.children.size == 3)
-        assert(outputOrdering.head.children.count(_.isInstanceOf[AttributeReference]) == 2)
+        // Sort order should have 2 childrens, not 4. This is because t1.id*2 and 2*t1.id are same
+        // and t2.id is not a valid ordering (the final plan doesn't output t2.id)
+        assert(outputOrdering.head.children.size == 2)
+        assert(outputOrdering.head.children.count(_.isInstanceOf[AttributeReference]) == 1)
         assert(outputOrdering.head.children.count(_.isInstanceOf[Multiply]) == 1)
       }
     }
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/ProjectedOrderingAndPartitioningSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/ProjectedOrderingAndPartitioningSuite.scala
index e4ecdb9c44595..f5839e9975602 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/ProjectedOrderingAndPartitioningSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/ProjectedOrderingAndPartitioningSuite.scala
@@ -177,4 +177,18 @@ class ProjectedOrderingAndPartitioningSuite
     val outputOrdering3 = df3.queryExecution.optimizedPlan.outputOrdering
     assert(outputOrdering3.size == 0)
   }
+
+  test("SPARK-42049: Improve AliasAwareOutputExpression - no alias but still prune expressions") {
+    val df = spark.range(2).select($"id" + 1 as "a", $"id" + 2 as "b")
+
+    val df1 = df.repartition($"a", $"b").selectExpr("a")
+    val outputPartitioning = stripAQEPlan(df1.queryExecution.executedPlan).outputPartitioning
+    assert(outputPartitioning.isInstanceOf[UnknownPartitioning])
+
+    val df2 = df.orderBy("a", "b").select("a")
+    val outputOrdering = df2.queryExecution.optimizedPlan.outputOrdering
+    assert(outputOrdering.size == 1)
+    assert(outputOrdering.head.child.asInstanceOf[Attribute].name == "a")
+    assert(outputOrdering.head.sameOrderExpressions.size == 0)
+  }
 }