diff --git a/MarkMpn.Sql4Cds.Engine/ExecutionPlan/NodeSchema.cs b/MarkMpn.Sql4Cds.Engine/ExecutionPlan/NodeSchema.cs
index 01999a90..d2e5b7d2 100644
--- a/MarkMpn.Sql4Cds.Engine/ExecutionPlan/NodeSchema.cs
+++ b/MarkMpn.Sql4Cds.Engine/ExecutionPlan/NodeSchema.cs
@@ -77,15 +77,24 @@ public NodeSchema(INodeSchema copy)
         /// <returns><c>true</c> if the column name exists, or <c>false</c> otherwise</returns>
         public bool ContainsColumn(string column, out string normalized)
         {
-            if (Schema.TryGetValue(column, out _))
+            if (Aliases.TryGetValue(column, out var names))
             {
-                normalized = Schema.Keys.Single(k => k.Equals(column, StringComparison.OrdinalIgnoreCase));
-                return true;
+                if (names.Count > 1)
+                {
+                    normalized = null;
+                    return false;
+                }
+
+                if (names.Count == 1)
+                {
+                    normalized = names[0];
+                    return true;
+                }
             }
 
-            if (Aliases.TryGetValue(column, out var names) && names.Count == 1)
+            if (Schema.TryGetValue(column, out _))
             {
-                normalized = names[0];
+                normalized = Schema.Keys.Single(k => k.Equals(column, StringComparison.OrdinalIgnoreCase));
                 return true;
             }
 
diff --git a/MarkMpn.Sql4Cds.Engine/ExecutionPlan/OpenJsonNode.cs b/MarkMpn.Sql4Cds.Engine/ExecutionPlan/OpenJsonNode.cs
index 8a1ed57b..afd0f9a9 100644
--- a/MarkMpn.Sql4Cds.Engine/ExecutionPlan/OpenJsonNode.cs
+++ b/MarkMpn.Sql4Cds.Engine/ExecutionPlan/OpenJsonNode.cs
@@ -92,9 +92,6 @@ public override IDataExecutionPlanNodeInternal FoldQuery(NodeCompilationContext
             _jsonExpression = Json.Compile(ecc);
             _pathExpression = Path?.Compile(ecc);
 
-            Json.GetType(ecc, out var jsonType);
-            _jsonCollation = (jsonType as SqlDataTypeReferenceWithCollation)?.Collation ?? context.PrimaryDataSource.DefaultCollation;
-
             return this;
         }
 
@@ -105,6 +102,13 @@ public override INodeSchema GetSchema(NodeCompilationContext context)
 
             if (Schema == null)
             {
+                if (_jsonCollation == null)
+                {
+                    var ecc = new ExpressionCompilationContext(context, null, null);
+                    Json.GetType(ecc, out var jsonType);
+                    _jsonCollation = (jsonType as SqlDataTypeReferenceWithCollation)?.Collation ?? context.PrimaryDataSource.DefaultCollation;
+                }
+
                 columns.Add(PrefixWithAlias("key", aliases), new ColumnDefinition(DataTypeHelpers.NVarChar(4000, _keyCollation, CollationLabel.Implicit), false, false));
                 columns.Add(PrefixWithAlias("value", aliases), new ColumnDefinition(DataTypeHelpers.NVarChar(Int32.MaxValue, _jsonCollation, CollationLabel.Implicit), true, false));
                 columns.Add(PrefixWithAlias("type", aliases), new ColumnDefinition(DataTypeHelpers.Int, false, false));
@@ -162,10 +166,7 @@ private string PrefixWithAlias(string name, IDictionary<string, IReadOnlyList<st
         {
             name = name.EscapeIdentifier();
 
-            if (Alias == null)
-                return name;
-
-            var fullName = Alias.EscapeIdentifier() + "." + name;
+            var fullName = Alias == null ? name : (Alias.EscapeIdentifier() + "." + name);
 
             if (aliases != null)
             {