Allow Group By of Joined table

Author: mythz

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -457,7 +457,18 @@ public virtual SqlExpression<T> GroupBy(string groupBy)
             return this;
         }
 
-        public virtual SqlExpression<T> GroupBy<TKey>(Expression<Func<T, TKey>> keySelector)
+        public virtual SqlExpression<T> GroupBy<Table>(Expression<Func<Table, object>> keySelector)
+        {
+            sep = string.Empty;
+            useFieldName = true;
+
+            var groupByKey = Visit(keySelector);
+            StripAliases(groupByKey as SelectList); // No "AS ColumnAlias" in GROUP BY, just the column names/expressions
+
+            return GroupBy(groupByKey.ToString());
+        }
+
+        public virtual SqlExpression<T> GroupBy(Expression<Func<T, object>> keySelector)
         {
             sep = string.Empty;
             useFieldName = true;

tests/ServiceStack.OrmLite.Tests/UseCase/ArtistTrackSqlExpressions.cs

@@ -1,4 +1,5 @@
-using NUnit.Framework;
+using System.Linq;
+using NUnit.Framework;
 using ServiceStack.OrmLite.Tests.Support;
 using ServiceStack.Text;
 
@@ -44,5 +45,20 @@ public void Can_Order_by_Property_Alias()
                 Assert.That(result[1993], Is.EqualTo(2));
             }
         }
+
+        [Test]
+        public void Can_Select_joined_table_with_Alias()
+        {
+            using (var db = CreateArtistAndTrackTablesWithData(OpenDbConnection()))
+            {
+                var tracksByYear = db.Dictionary<string, int>(db.From<Track>()
+                    .Join<Artist>()
+                    .GroupBy<Artist>(x => x.Name)
+                    .Select<Artist>(x => new { x.Name, Count = Sql.Count("*") }));
+
+                Assert.That(tracksByYear.Count, Is.EqualTo(4));
+                Assert.That(tracksByYear.Map(x => x.Value).Sum(), Is.EqualTo(8));
+            }
+        }
     }
 }