Supquery support As

Src/Asp.Net/SqlSugar/ExpressionsToSql/Subquery/Items/SubAs.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace SqlSugar 
+{
+    public class SubAs : ISubOperation
+    {
+        public bool HasWhere
+        {
+            get; set;
+        }
+
+        public string Name
+        {
+            get
+            {
+                return "AS";
+            }
+        }
+
+        public Expression Expression
+        {
+            get; set;
+        }
+
+
+        public int Sort
+        {
+            get
+            {
+                return 200;
+            }
+        }
+
+        public ExpressionContext Context
+        {
+            get; set;
+        }
+
+        public string GetValue(Expression expression = null)
+        {
+            var exp = expression as MethodCallExpression;
+            var expString=  SubTools.GetMethodValue(this.Context, exp.Arguments[0], ResolveExpressType.WhereSingle)?.Trim();
+            var result =   this.Context.Parameters.First(it => it.ParameterName == expString).Value+"";
+            return "$SubAs:"+result;
+        }
+    }
+}

Src/Asp.Net/SqlSugar/ExpressionsToSql/Subquery/SubResolve.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Text;
+using System.Text.RegularExpressions;
 
 namespace SqlSugar
 {
@@ -16,6 +17,7 @@ namespace SqlSugar
     {
         List<MethodCallExpression> allMethods = new List<MethodCallExpression>();
         private ExpressionContext context = null;
+        private string subKey = "$SubAs:";
         private bool hasWhere;
         public SubResolve(MethodCallExpression expression, ExpressionContext context, Expression oppsiteExpression)
         {
@@ -85,14 +87,32 @@ namespace SqlSugar
                 currentExpression = addItem;
             }
         }
-
         public string GetSql()
         {
             List<string> subItems = GetSubItems();
-            var sql = string.Join(UtilConstants.Space, subItems);
+            var sqlItems = subItems.Where(it => !it.StartsWith(subKey)).ToList();
+            var asItems = subItems.Where(it => it.StartsWith(subKey)).ToList();
+            if (asItems.Any())
+            {
+                GetSubAs(sqlItems, asItems);
+            }
+            var sql = string.Join(UtilConstants.Space, sqlItems);
             return this.context.DbMehtods.Pack(sql);
         }
 
+        private void GetSubAs(List<string> sqlItems, List<string> asItems)
+        {
+            for (int i = 0; i < sqlItems.Count; i++)
+            {
+                if (sqlItems[i].StartsWith("FROM " + this.context.SqlTranslationLeft))
+                {
+                    var asName = this.context.GetTranslationTableName(asItems.First().Replace(subKey, ""), false);
+                    var repKey = $"\\{this.context.SqlTranslationLeft}.+\\{this.context.SqlTranslationRight}";
+                    sqlItems[i] = Regex.Replace(sqlItems[i], repKey, asName);
+                }
+            }
+        }
+
         private List<string> GetSubItems()
         {
             var isubList = this.allMethods.Select(exp =>

Src/Asp.Net/SqlSugar/ExpressionsToSql/Subquery/SubTools.cs

@@ -31,7 +31,8 @@ namespace SqlSugar
                                                     new SubAvg(){ Context=Context },
                                                     new SubOrderBy(){ Context=Context },
                                                     new SubOrderByDesc(){ Context=Context },
-                                                    new SubGroupBy(){ Context=Context}
+                                                    new SubGroupBy(){ Context=Context},
+                                                    new SubAs(){Context=Context}
                                                 };
         }
 

Src/Asp.Net/SqlSugar/ExpressionsToSql/Subquery/Subquerable.cs

@@ -10,6 +10,10 @@ namespace SqlSugar
     public class Subqueryable<T> where T : class, new()
     {
 
+        public Subqueryable<T> AS(string tableName) 
+        {
+            return this;
+        }
         public Subqueryable<T> InnerJoin<JoinType>(Func<T, JoinType, bool> expression)
         {
             return this;

Src/Asp.Net/SqlSugar/SqlSugar.csproj

@@ -88,6 +88,7 @@
     <Compile Include="Abstract\FilterProvider\FilterProvider.cs" />
     <Compile Include="Abstract\InsertableProvider\InsertableProvider.cs" />
     <Compile Include="Abstract\DeleteProvider\DeleteableProvider.cs" />
+    <Compile Include="ExpressionsToSql\Subquery\Items\SubAs.cs" />
     <Compile Include="Interface\IParameterInsertable.cs" />
     <Compile Include="Abstract\InsertableProvider\ParameterInsertable.cs" />
     <Compile Include="Abstract\Reportable\ReportableProvider.cs" />