Optimize split table

Src/Asp.Net/MySqlTest/Demo/DemoN_SplitTable.cs

@@ -68,6 +68,9 @@ namespace OrmTest
             Console.WriteLine();
             ////强制分表类型
             var x4 = db.Insertable(new OrderSpliteTest() { Name = "A" ,Time=DateTime.Now.AddDays(-1) }).SplitTable().ExecuteCommand();
+
+            var tableName21 = db.SplitHelper<OrderSpliteTest>().GetTableName(DateTime.Now.AddDays(-111));
+            var listNull = db.Queryable<OrderSpliteTest>().SplitTable(ta => ta.InTableNames(tableName21)).ToList();
             Console.WriteLine("#### CodeFirst end ####");
         }
 

Src/Asp.Net/PgSqlTest/Demo/DemoN_SplitTable.cs

@@ -68,6 +68,10 @@ namespace OrmTest
             Console.WriteLine();
             ////强制分表类型
             var x4 = db.Insertable(new OrderSpliteTest() { Name = "A" ,Time=DateTime.Now.AddDays(-1) }).SplitTable().ExecuteCommand();
+
+
+            var tableName21 = db.SplitHelper<OrderSpliteTest>().GetTableName(DateTime.Now.AddDays(-111));
+            var listNull = db.Queryable<OrderSpliteTest>().SplitTable(ta => ta.InTableNames(tableName21)).ToList();
             Console.WriteLine("#### CodeFirst end ####");
         }
 

Src/Asp.Net/SqlServerTest/Demo/DemoN_SplitTable.cs

@@ -48,7 +48,10 @@ namespace OrmTest
            
             Console.WriteLine();
 
-            var tableName = db.SplitHelper<OrderSpliteTest>().GetTableName(DateTime.Now.AddDays(-1));
+            var tableName = db.SplitHelper<OrderSpliteTest>().GetTableName(DateTime.Now.AddDays(-111));
+
+            var listNull= db.Queryable<OrderSpliteTest>().SplitTable(ta => ta.InTableNames(tableName)).ToList();
+
             var tableName2 = db.SplitHelper(new OrderSpliteTest() {  Time=DateTime.Now}).GetTableNames();
             var tableName3 = db.SplitHelper(new List<OrderSpliteTest> {
               new OrderSpliteTest() { Time = DateTime.Now },

Src/Asp.Net/SqlSugar/Abstract/QueryableProvider/QueryableProvider.cs

@@ -931,11 +931,19 @@ namespace SqlSugar
             {
                 tableQueryables.Add(this.Clone().AS(item.TableName));
             }
-            Check.Exception(tableQueryables.Count == 0, ErrorMessage.GetThrowMessage("SplitTable error . There are no tables after filtering", "SplitTable没有筛选出分表，请检查条件和数据库中的表"));
-            var unionall = this.Context._UnionAll(tableQueryables.ToArray());
+            if (tableQueryables.Count == 0)
+            {
+                var result= this.Context.SqlQueryable<object>("-- No table ").Select<T>();
+                result.QueryBuilder.SelectValue = null;
+                return result;
+            }
+            else
+            {
+                var unionall = this.Context._UnionAll(tableQueryables.ToArray());
+                return unionall;
+            }
             //var values= unionall.QueryBuilder.GetSelectValue;
             //unionall.QueryBuilder.SelectValue = values;
-            return unionall;
         }
         public ISugarQueryable<T> Distinct()
         {