Add SqlFunc.Left Right LeftPad

Src/Asp.Net/SqlSugar/ExpressionsToSql/DbMethods/DefaultDbMethod.cs

@@ -1031,5 +1031,25 @@ namespace SqlSugar
             var parameterNameB = mode.Args[1].MemberName;
             return $" CASE WHEN LEFT({parameterNameA}, 1) = {parameterNameB} THEN RIGHT({parameterNameA}, LEN({parameterNameA}) - 1) ELSE {parameterNameA} END  ";
         }
+
+        public virtual string Left(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            return $" LEFT({parameterNameA},{parameterNameB}) ";
+        }
+        public virtual string Right(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            return $" RIGHT({parameterNameA},{parameterNameB}) ";
+        }
+        public virtual string PadLeft(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            var parameterNameC = mode.Args[2].MemberName;
+            return $" LPAD({parameterNameA},{parameterNameB},{parameterNameC}) ";
+        }
     }
 }

Src/Asp.Net/SqlSugar/ExpressionsToSql/DbMethods/IDbMethods.cs

@@ -116,5 +116,8 @@ namespace SqlSugar
         string WeekOfYear(MethodCallExpressionModel mode);
         string TrimEnd(MethodCallExpressionModel mode);    
         string TrimStart(MethodCallExpressionModel mode);
+        string Left(MethodCallExpressionModel mode);
+        string Right(MethodCallExpressionModel mode);
+        string PadLeft(MethodCallExpressionModel mode);
     }
 }

Src/Asp.Net/SqlSugar/ExpressionsToSql/DbMethods/SqlFunc.cs

@@ -13,6 +13,18 @@ namespace SqlSugar
         {
             throw new NotSupportedException("Can only be used in expressions");
         }
+        public static string Left(string value,int number) 
+        {
+            throw new NotSupportedException("Can only be used in expressions");
+        }
+        public static string Right(string value,int number)
+        {
+            throw new NotSupportedException("Can only be used in expressions");
+        }
+        public static string PadLeft(string value,int number, char padChar)
+        {
+            throw new NotSupportedException("Can only be used in expressions");
+        }
         public static bool Like(string fieldName, string likeValue) 
         {
             throw new NotSupportedException("Can only be used in expressions");

Src/Asp.Net/SqlSugar/Realization/Dm/SqlBuilder/DmExpressionContext.cs

@@ -240,5 +240,18 @@ namespace SqlSugar
             var parameterNameB = mode.Args[1].MemberName;
             return $" LTRIM({parameterNameA}, {parameterNameB}) ";
         }
+
+        public override string Left(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            return $" SUBSTR({parameterNameA}, 1, {parameterNameB})  ";
+        }
+        public override string Right(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            return $" SUBSTR({parameterNameA}, -2, {parameterNameB})  ";
+        }
     }
 }

Src/Asp.Net/SqlSugar/Realization/Oracle/SqlBuilder/OracleExpressionContext.cs

@@ -366,5 +366,17 @@ namespace SqlSugar
             var parameterNameB = mode.Args[1].MemberName;
             return $" LTRIM({parameterNameA}, {parameterNameB}) ";
         }
+        public override string Left(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            return $" SUBSTR({parameterNameA}, 1, {parameterNameB})  ";
+        }
+        public override string Right(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            return $" SUBSTR({parameterNameA}, -2, {parameterNameB})  ";
+        }
     }
 }

Src/Asp.Net/SqlSugar/Realization/SqlServer/SqlBuilder/SqlServerExpressionContext.cs

@@ -122,6 +122,14 @@ namespace SqlSugar
             var parameterNameB = mode.Args[1].MemberName;
             return $" CASE WHEN LEFT({parameterNameA}, 1) = {parameterNameB} THEN RIGHT({parameterNameA}, LEN({parameterNameA}) - 1) ELSE {parameterNameA} END ";
         }
+
+        public override string PadLeft(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            var parameterNameC = mode.Args[2].MemberName;
+            return $" CONCAT(REPLICATE({parameterNameC}, {parameterNameB} - LEN({parameterNameA})), {parameterNameA})  ";
+        }
     }
 
 

Src/Asp.Net/SqlSugar/Realization/Sqlite/SqlBuilder/SqliteExpressionContext.cs

@@ -297,5 +297,27 @@ namespace SqlSugar
             var parameterNameB = mode.Args[1].MemberName;
             return $"  CASE WHEN SUBSTR({parameterNameA}, 1, 1) ={parameterNameB} THEN SUBSTR({parameterNameA}, 2) ELSE {parameterNameA} END ";
         }
+
+        public override string PadLeft(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            var parameterNameC = mode.Args[2].MemberName;
+            var value = new string[mode.Args[1].MemberValue.ObjToInt()].Select(it=> parameterNameC); 
+            return $"substr({string.Join("||", value)} || {parameterNameA}, {parameterNameB}*-1)  ";
+        }
+
+        public override string Left(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            return $" SUBSTR({parameterNameA}, 1, {parameterNameB})  ";
+        }
+        public override string Right(MethodCallExpressionModel mode)
+        {
+            var parameterNameA = mode.Args[0].MemberName;
+            var parameterNameB = mode.Args[1].MemberName;
+            return $" SUBSTR({parameterNameA}, -2, {parameterNameB})  ";
+        }
     }
 }