diff --git a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Oracle/OracleExpression/DateTimeTest.cs b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Oracle/OracleExpression/DateTimeTest.cs
index 2e566ddd..9d3473f7 100644
--- a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Oracle/OracleExpression/DateTimeTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Oracle/OracleExpression/DateTimeTest.cs
@@ -41,6 +41,52 @@ namespace FreeSql.Tests.Odbc.OracleExpression
             public List<TestTypeInfo> Types { get; set; }
             public DateTime Time2 { get; set; }
         }
+
+        [Fact]
+        public void this_ToString()
+        {
+            var data = new List<object>();
+            data.Add(select.Where(a => a.CreateTime.ToString().Equals(DateTime.Now.ToString())).ToList());
+            data.Add(select.Where(a => a.Type.Time.AddYears(1).ToString().Equals(DateTime.Now.ToString())).ToList());
+            data.Add(select.Where(a => a.Type.Parent.Time2.AddYears(1).ToString().Equals(DateTime.Now.ToString())).ToList());
+            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a.`Title` as4, a.`CreateTime` as5 
+            //FROM `tb_topic111333` a 
+            //WHERE ((date_format(a.`CreateTime`, '%Y-%m-%d %H:%i:%s.%f') = now()));
+
+            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a__Type.`Guid` as4, a__Type.`ParentId` as5, a__Type.`Name` as6, a__Type.`Time` as7, a.`Title` as8, a.`CreateTime` as9 
+            //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type 
+            //WHERE ((date_format(date_add(a__Type.`Time`, interval (1) year), '%Y-%m-%d %H:%i:%s.%f') = now()));
+
+            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a__Type.`Guid` as4, a__Type.`ParentId` as5, a__Type.`Name` as6, a__Type.`Time` as7, a.`Title` as8, a.`CreateTime` as9 
+            //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type, `TestTypeParentInfo23123` a__Type__Parent 
+            //WHERE ((date_format(date_add(a__Type__Parent.`Time2`, interval (1) year), '%Y-%m-%d %H:%i:%s.%f') = now()))
+
+            g.oracle.Insert(new Topic()).ExecuteAffrows();
+            var dtn = DateTime.Parse("2020-1-1 0:0:0");
+            var dts = Enumerable.Range(1, 12).Select(a => dtn.AddMonths(a))
+                .Concat(Enumerable.Range(1, 31).Select(a => dtn.AddDays(a)))
+                .Concat(Enumerable.Range(1, 24).Select(a => dtn.AddHours(a)))
+                .Concat(Enumerable.Range(1, 60).Select(a => dtn.AddMinutes(a)))
+                .Concat(Enumerable.Range(1, 60).Select(a => dtn.AddSeconds(a)));
+            foreach (var dt in dts)
+            {
+                Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss.ffffff"), select.First(a => dt.ToString()));
+                Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss"), select.First(a => dt.ToString("yyyy-MM-dd HH:mm:ss")));
+                Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm"), select.First(a => dt.ToString("yyyy-MM-dd HH:mm")));
+                Assert.Equal(dt.ToString("yyyy-MM-dd HH"), select.First(a => dt.ToString("yyyy-MM-dd HH")));
+                Assert.Equal(dt.ToString("yyyy-MM-dd"), select.First(a => dt.ToString("yyyy-MM-dd")));
+                Assert.Equal(dt.ToString("yyyy-MM"), select.First(a => dt.ToString("yyyy-MM")));
+                Assert.Equal(dt.ToString("yyyyMMddHHmmss"), select.First(a => dt.ToString("yyyyMMddHHmmss")));
+                Assert.Equal(dt.ToString("yyyyMMddHHmm"), select.First(a => dt.ToString("yyyyMMddHHmm")));
+                Assert.Equal(dt.ToString("yyyyMMddHH"), select.First(a => dt.ToString("yyyyMMddHH")));
+                Assert.Equal(dt.ToString("yyyyMMdd"), select.First(a => dt.ToString("yyyyMMdd")));
+                Assert.Equal(dt.ToString("yyyyMM"), select.First(a => dt.ToString("yyyyMM")));
+                Assert.Equal(dt.ToString("yyyy"), select.First(a => dt.ToString("yyyy")));
+                Assert.Equal(dt.ToString("HH:mm:ss"), select.First(a => dt.ToString("HH:mm:ss")));
+                Assert.Equal(dt.ToString("yyyy MM dd HH mm ss yy M d H hh h"), select.First(a => dt.ToString("yyyy MM dd HH mm ss yy M d H hh h")));
+                Assert.Equal(dt.ToString("yyyy MM dd HH mm ss yy M d H hh h m s"), select.First(a => dt.ToString("yyyy MM dd HH mm ss yy M d H hh h m s")));
+            }
+        }
         [Fact]
         public void Now()
         {
@@ -587,26 +633,6 @@ namespace FreeSql.Tests.Odbc.OracleExpression
             //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type, `TestTypeParentInfo23123` a__Type__Parent 
             //WHERE ((date_add(a__Type__Parent.`Time2`, interval (1) year) = now()))
         }
-        [Fact]
-        public void this_ToString()
-        {
-            var data = new List<object>();
-            data.Add(select.Where(a => a.CreateTime.ToString().Equals(DateTime.Now)).ToList());
-            data.Add(select.Where(a => a.Type.Time.AddYears(1).ToString().Equals(DateTime.Now)).ToList());
-            data.Add(select.Where(a => a.Type.Parent.Time2.AddYears(1).ToString().Equals(DateTime.Now)).ToList());
-            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a.`Title` as4, a.`CreateTime` as5 
-            //FROM `tb_topic111333` a 
-            //WHERE ((date_format(a.`CreateTime`, '%Y-%m-%d %H:%i:%s.%f') = now()));
-
-            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a__Type.`Guid` as4, a__Type.`ParentId` as5, a__Type.`Name` as6, a__Type.`Time` as7, a.`Title` as8, a.`CreateTime` as9 
-            //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type 
-            //WHERE ((date_format(date_add(a__Type.`Time`, interval (1) year), '%Y-%m-%d %H:%i:%s.%f') = now()));
-
-            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a__Type.`Guid` as4, a__Type.`ParentId` as5, a__Type.`Name` as6, a__Type.`Time` as7, a.`Title` as8, a.`CreateTime` as9 
-            //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type, `TestTypeParentInfo23123` a__Type__Parent 
-            //WHERE ((date_format(date_add(a__Type__Parent.`Time2`, interval (1) year), '%Y-%m-%d %H:%i:%s.%f') = now()))
-        }
-
         [Fact]
         public void DateTime_Compare()
         {
diff --git a/FreeSql.Tests/FreeSql.Tests/Oracle/OracleExpression/DateTimeTest.cs b/FreeSql.Tests/FreeSql.Tests/Oracle/OracleExpression/DateTimeTest.cs
index 0fe69d3a..020968f2 100644
--- a/FreeSql.Tests/FreeSql.Tests/Oracle/OracleExpression/DateTimeTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests/Oracle/OracleExpression/DateTimeTest.cs
@@ -41,6 +41,52 @@ namespace FreeSql.Tests.OracleExpression
             public List<TestTypeInfo> Types { get; set; }
             public DateTime Time2 { get; set; }
         }
+
+        [Fact]
+        public void this_ToString()
+        {
+            var data = new List<object>();
+            data.Add(select.Where(a => a.CreateTime.ToString().Equals(DateTime.Now.ToString())).ToList());
+            data.Add(select.Where(a => a.Type.Time.AddYears(1).ToString().Equals(DateTime.Now.ToString())).ToList());
+            data.Add(select.Where(a => a.Type.Parent.Time2.AddYears(1).ToString().Equals(DateTime.Now.ToString())).ToList());
+            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a.`Title` as4, a.`CreateTime` as5 
+            //FROM `tb_topic111333` a 
+            //WHERE ((date_format(a.`CreateTime`, '%Y-%m-%d %H:%i:%s.%f') = now()));
+
+            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a__Type.`Guid` as4, a__Type.`ParentId` as5, a__Type.`Name` as6, a__Type.`Time` as7, a.`Title` as8, a.`CreateTime` as9 
+            //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type 
+            //WHERE ((date_format(date_add(a__Type.`Time`, interval (1) year), '%Y-%m-%d %H:%i:%s.%f') = now()));
+
+            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a__Type.`Guid` as4, a__Type.`ParentId` as5, a__Type.`Name` as6, a__Type.`Time` as7, a.`Title` as8, a.`CreateTime` as9 
+            //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type, `TestTypeParentInfo23123` a__Type__Parent 
+            //WHERE ((date_format(date_add(a__Type__Parent.`Time2`, interval (1) year), '%Y-%m-%d %H:%i:%s.%f') = now()))
+
+            g.oracle.Insert(new Topic()).ExecuteAffrows();
+            var dtn = DateTime.Parse("2020-1-1 0:0:0");
+            var dts = Enumerable.Range(1, 12).Select(a => dtn.AddMonths(a))
+                .Concat(Enumerable.Range(1, 31).Select(a => dtn.AddDays(a)))
+                .Concat(Enumerable.Range(1, 24).Select(a => dtn.AddHours(a)))
+                .Concat(Enumerable.Range(1, 60).Select(a => dtn.AddMinutes(a)))
+                .Concat(Enumerable.Range(1, 60).Select(a => dtn.AddSeconds(a)));
+            foreach (var dt in dts)
+            {
+                Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss.ffffff"), select.First(a => dt.ToString()));
+                Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss"), select.First(a => dt.ToString("yyyy-MM-dd HH:mm:ss")));
+                Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm"), select.First(a => dt.ToString("yyyy-MM-dd HH:mm")));
+                Assert.Equal(dt.ToString("yyyy-MM-dd HH"), select.First(a => dt.ToString("yyyy-MM-dd HH")));
+                Assert.Equal(dt.ToString("yyyy-MM-dd"), select.First(a => dt.ToString("yyyy-MM-dd")));
+                Assert.Equal(dt.ToString("yyyy-MM"), select.First(a => dt.ToString("yyyy-MM")));
+                Assert.Equal(dt.ToString("yyyyMMddHHmmss"), select.First(a => dt.ToString("yyyyMMddHHmmss")));
+                Assert.Equal(dt.ToString("yyyyMMddHHmm"), select.First(a => dt.ToString("yyyyMMddHHmm")));
+                Assert.Equal(dt.ToString("yyyyMMddHH"), select.First(a => dt.ToString("yyyyMMddHH")));
+                Assert.Equal(dt.ToString("yyyyMMdd"), select.First(a => dt.ToString("yyyyMMdd")));
+                Assert.Equal(dt.ToString("yyyyMM"), select.First(a => dt.ToString("yyyyMM")));
+                Assert.Equal(dt.ToString("yyyy"), select.First(a => dt.ToString("yyyy")));
+                Assert.Equal(dt.ToString("HH:mm:ss"), select.First(a => dt.ToString("HH:mm:ss")));
+                Assert.Equal(dt.ToString("yyyy MM dd HH mm ss yy M d H hh h"), select.First(a => dt.ToString("yyyy MM dd HH mm ss yy M d H hh h")));
+                Assert.Equal(dt.ToString("yyyy MM dd HH mm ss yy M d H hh h m s"), select.First(a => dt.ToString("yyyy MM dd HH mm ss yy M d H hh h m s")));
+            }
+        }
         [Fact]
         public void Now()
         {
@@ -587,26 +633,6 @@ namespace FreeSql.Tests.OracleExpression
             //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type, `TestTypeParentInfo23123` a__Type__Parent 
             //WHERE ((date_add(a__Type__Parent.`Time2`, interval (1) year) = now()))
         }
-        [Fact]
-        public void this_ToString()
-        {
-            var data = new List<object>();
-            data.Add(select.Where(a => a.CreateTime.ToString().Equals(DateTime.Now)).ToList());
-            data.Add(select.Where(a => a.Type.Time.AddYears(1).ToString().Equals(DateTime.Now)).ToList());
-            data.Add(select.Where(a => a.Type.Parent.Time2.AddYears(1).ToString().Equals(DateTime.Now)).ToList());
-            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a.`Title` as4, a.`CreateTime` as5 
-            //FROM `tb_topic111333` a 
-            //WHERE ((date_format(a.`CreateTime`, '%Y-%m-%d %H:%i:%s.%f') = now()));
-
-            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a__Type.`Guid` as4, a__Type.`ParentId` as5, a__Type.`Name` as6, a__Type.`Time` as7, a.`Title` as8, a.`CreateTime` as9 
-            //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type 
-            //WHERE ((date_format(date_add(a__Type.`Time`, interval (1) year), '%Y-%m-%d %H:%i:%s.%f') = now()));
-
-            //SELECT a.`Id` as1, a.`Clicks` as2, a.`TypeGuid` as3, a__Type.`Guid` as4, a__Type.`ParentId` as5, a__Type.`Name` as6, a__Type.`Time` as7, a.`Title` as8, a.`CreateTime` as9 
-            //FROM `tb_topic111333` a, `TestTypeInfo333` a__Type, `TestTypeParentInfo23123` a__Type__Parent 
-            //WHERE ((date_format(date_add(a__Type__Parent.`Time2`, interval (1) year), '%Y-%m-%d %H:%i:%s.%f') = now()))
-        }
-
         [Fact]
         public void DateTime_Compare()
         {
diff --git a/Providers/FreeSql.Provider.Odbc/MySql/OdbcMySqlExpression.cs b/Providers/FreeSql.Provider.Odbc/MySql/OdbcMySqlExpression.cs
index 9befd68f..5cb20008 100644
--- a/Providers/FreeSql.Provider.Odbc/MySql/OdbcMySqlExpression.cs
+++ b/Providers/FreeSql.Provider.Odbc/MySql/OdbcMySqlExpression.cs
@@ -1,8 +1,6 @@
 using FreeSql.Internal;
-using FreeSql.Internal.Model;
 using System;
 using System.Collections;
-using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Text;
diff --git a/Providers/FreeSql.Provider.Odbc/Oracle/OdbcOracleExpression.cs b/Providers/FreeSql.Provider.Odbc/Oracle/OdbcOracleExpression.cs
index d09da364..2795c374 100644
--- a/Providers/FreeSql.Provider.Odbc/Oracle/OdbcOracleExpression.cs
+++ b/Providers/FreeSql.Provider.Odbc/Oracle/OdbcOracleExpression.cs
@@ -1,11 +1,10 @@
 using FreeSql.Internal;
-using FreeSql.Internal.Model;
 using System;
 using System.Collections;
-using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Text;
+using System.Text.RegularExpressions;
 
 namespace FreeSql.Odbc.Oracle
 {
@@ -398,7 +397,57 @@ namespace FreeSql.Odbc.Oracle
                         break;
                     case "Equals": return $"({left} = {args1})";
                     case "CompareTo": return $"extract(day from ({left}-({args1})))";
-                    case "ToString": return exp.Arguments.Count == 0 ? $"to_char({left},'YYYY-MM-DD HH24:MI:SS.FF6')" : null;
+                    case "ToString":
+                        if (left.StartsWith("'") || left.EndsWith("'")) left = $"to_timestamp({left},'YYYY-MM-DD HH24:MI:SS.FF6')";
+                        if (exp.Arguments.Count == 0) return $"to_char({left},'YYYY-MM-DD HH24:MI:SS.FF6')";
+                        switch (args1)
+                        {
+                            case "'yyyy-MM-dd HH:mm:ss'": return $"to_char({left},'YYYY-MM-DD HH24:MI:SS')";
+                            case "'yyyy-MM-dd HH:mm'": return $"to_char({left},'YYYY-MM-DD HH24:MI')";
+                            case "'yyyy-MM-dd HH'": return $"to_char({left},'YYYY-MM-DD HH24')";
+                            case "'yyyy-MM-dd'": return $"to_char({left},'YYYY-MM-DD')";
+                            case "'yyyy-MM'": return $"to_char({left},'YYYY-MM')";
+                            case "'yyyyMMddHHmmss'": return $"to_char({left},'YYYYMMDDHH24MISS')";
+                            case "'yyyyMMddHHmm'": return $"to_char({left},'YYYYMMDDHH24MI')";
+                            case "'yyyyMMddHH'": return $"to_char({left},'YYYYMMDDHH24')";
+                            case "'yyyyMMdd'": return $"to_char({left},'YYYYMMDD')";
+                            case "'yyyyMM'": return $"to_char({left},'YYYYMM')";
+                            case "'yyyy'": return $"to_char({left},'YYYY')";
+                            case "'HH:mm:ss'": return $"to_char({left},'HH24:MI:SS')";
+                        }
+                        args1 = Regex.Replace(args1, "(yyyy|yy|MM|dd|HH|hh|mm|ss|tt)", m =>
+                        {
+                            switch (m.Groups[1].Value)
+                            {
+                                case "yyyy": return $"YYYY";
+                                case "yy": return $"YY";
+                                case "MM": return $"%_a1";
+                                case "dd": return $"%_a2";
+                                case "HH": return $"%_a3";
+                                case "hh": return $"%_a4";
+                                case "mm": return $"%_a5";
+                                case "ss": return $"SS";
+                                case "tt": return $"%_a6";
+                            }
+                            return m.Groups[0].Value;
+                        });
+                        var isMatched = false;
+                        args1 = Regex.Replace(args1, "(M|d|H|h|m|s|t)", m =>
+                        {
+                            isMatched = true;
+                            switch (m.Groups[1].Value)
+                            {
+                                case "M": return $"') || ltrim(to_char({left},'MM'),'0') || to_char({left},'";
+                                case "d": return $"') || case when substr(to_char({left},'DD'),1,1) = '0' then substr(to_char({left},'DD'),2,1) else to_char({left},'DD') end || to_char({left},'";
+                                case "H": return $"') || case when substr(to_char({left},'HH24'),1,1) = '0' then substr(to_char({left},'HH24'),2,1) else to_char({left},'HH24') end || to_char({left},'";
+                                case "h": return $"') || case when substr(to_char({left},'HH12'),1,1) = '0' then substr(to_char({left},'HH12'),2,1) else to_char({left},'HH12') end || to_char({left},'";
+                                case "m": return $"') || case when substr(to_char({left},'MI'),1,1) = '0' then substr(to_char({left},'MI'),2,1) else to_char({left},'MI') end || to_char({left},'";
+                                case "s": return $"') || case when substr(to_char({left},'SS'),1,1) = '0' then substr(to_char({left},'SS'),2,1) else to_char({left},'SS') end || to_char({left},'";
+                                case "t": return $"') || rtrim(to_char({left},'AM'),'M') || to_char({left},'";
+                            }
+                            return m.Groups[0].Value;
+                        }).Replace("%_a1", "MM").Replace("%_a2", "DD").Replace("%_a3", "HH24").Replace("%_a4", "HH12").Replace("%_a5", "MI").Replace("%_a6", "AM");
+                        return isMatched == false ? $"to_char({left},{args1})" : $"(to_char({left},{args1}))".Replace($"to_char({left},'')", "''");
                 }
             }
             return null;
diff --git a/Providers/FreeSql.Provider.Odbc/PostgreSQL/OdbcPostgreSQLExpression.cs b/Providers/FreeSql.Provider.Odbc/PostgreSQL/OdbcPostgreSQLExpression.cs
index a6b53a6b..4ab8f9fd 100644
--- a/Providers/FreeSql.Provider.Odbc/PostgreSQL/OdbcPostgreSQLExpression.cs
+++ b/Providers/FreeSql.Provider.Odbc/PostgreSQL/OdbcPostgreSQLExpression.cs
@@ -1,5 +1,4 @@
 using FreeSql.Internal;
-using FreeSql.Internal.Model;
 using System;
 using System.Collections;
 using System.Collections.Generic;
@@ -485,7 +484,7 @@ namespace FreeSql.Odbc.PostgreSQL
                     case "Equals": return $"({left} = ({args1})::timestamp)";
                     case "CompareTo": return $"extract(epoch from ({left})::timestamp-({args1})::timestamp)";
                     case "ToString":
-                        left = $"({left})::timestamp";
+                        if (left.EndsWith("::timestamp") == false) left = $"({left})::timestamp";
                         if (exp.Arguments.Count == 0) return $"to_char({left},'YYYY-MM-DD HH24:MI:SS.US')";
                         switch (args1)
                         {
diff --git a/Providers/FreeSql.Provider.Odbc/SqlServer/OdbcSqlServerExpression.cs b/Providers/FreeSql.Provider.Odbc/SqlServer/OdbcSqlServerExpression.cs
index 95843601..086a6daf 100644
--- a/Providers/FreeSql.Provider.Odbc/SqlServer/OdbcSqlServerExpression.cs
+++ b/Providers/FreeSql.Provider.Odbc/SqlServer/OdbcSqlServerExpression.cs
@@ -374,7 +374,7 @@ namespace FreeSql.Odbc.SqlServer
                     case "Equals": return $"({left} = {args1})";
                     case "CompareTo": return $"datediff(second,{args1},{left})";
                     case "ToString":
-                        left = $"cast({left} as datetime)";
+                        if (left.EndsWith(" as datetime)") == false) left = $"cast({left} as datetime)";
                         if (exp.Arguments.Count == 0) return $"convert(varchar, {left}, 121)";
                         switch (args1.TrimStart('N'))
                         {
diff --git a/Providers/FreeSql.Provider.Oracle/OracleExpression.cs b/Providers/FreeSql.Provider.Oracle/OracleExpression.cs
index 5169f563..2029c68e 100644
--- a/Providers/FreeSql.Provider.Oracle/OracleExpression.cs
+++ b/Providers/FreeSql.Provider.Oracle/OracleExpression.cs
@@ -1,11 +1,10 @@
 using FreeSql.Internal;
-using FreeSql.Internal.Model;
 using System;
 using System.Collections;
-using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Text;
+using System.Text.RegularExpressions;
 
 namespace FreeSql.Oracle
 {
@@ -398,7 +397,57 @@ namespace FreeSql.Oracle
                         break;
                     case "Equals": return $"({left} = {args1})";
                     case "CompareTo": return $"extract(day from ({left}-({args1})))";
-                    case "ToString": return exp.Arguments.Count == 0 ? $"to_char({left},'YYYY-MM-DD HH24:MI:SS.FF6')" : null;
+                    case "ToString":
+                        if (left.StartsWith("'") || left.EndsWith("'")) left = $"to_timestamp({left},'YYYY-MM-DD HH24:MI:SS.FF6')";
+                        if (exp.Arguments.Count == 0) return $"to_char({left},'YYYY-MM-DD HH24:MI:SS.FF6')";
+                        switch (args1)
+                        {
+                            case "'yyyy-MM-dd HH:mm:ss'": return $"to_char({left},'YYYY-MM-DD HH24:MI:SS')";
+                            case "'yyyy-MM-dd HH:mm'": return $"to_char({left},'YYYY-MM-DD HH24:MI')";
+                            case "'yyyy-MM-dd HH'": return $"to_char({left},'YYYY-MM-DD HH24')";
+                            case "'yyyy-MM-dd'": return $"to_char({left},'YYYY-MM-DD')";
+                            case "'yyyy-MM'": return $"to_char({left},'YYYY-MM')";
+                            case "'yyyyMMddHHmmss'": return $"to_char({left},'YYYYMMDDHH24MISS')";
+                            case "'yyyyMMddHHmm'": return $"to_char({left},'YYYYMMDDHH24MI')";
+                            case "'yyyyMMddHH'": return $"to_char({left},'YYYYMMDDHH24')";
+                            case "'yyyyMMdd'": return $"to_char({left},'YYYYMMDD')";
+                            case "'yyyyMM'": return $"to_char({left},'YYYYMM')";
+                            case "'yyyy'": return $"to_char({left},'YYYY')";
+                            case "'HH:mm:ss'": return $"to_char({left},'HH24:MI:SS')";
+                        }
+                        args1 = Regex.Replace(args1, "(yyyy|yy|MM|dd|HH|hh|mm|ss|tt)", m =>
+                        {
+                            switch (m.Groups[1].Value)
+                            {
+                                case "yyyy": return $"YYYY";
+                                case "yy": return $"YY";
+                                case "MM": return $"%_a1";
+                                case "dd": return $"%_a2";
+                                case "HH": return $"%_a3";
+                                case "hh": return $"%_a4";
+                                case "mm": return $"%_a5";
+                                case "ss": return $"SS";
+                                case "tt": return $"%_a6";
+                            }
+                            return m.Groups[0].Value;
+                        });
+                        var isMatched = false;
+                        args1 = Regex.Replace(args1, "(M|d|H|h|m|s|t)", m =>
+                        {
+                            isMatched = true;
+                            switch (m.Groups[1].Value)
+                            {
+                                case "M": return $"') || ltrim(to_char({left},'MM'),'0') || to_char({left},'";
+                                case "d": return $"') || case when substr(to_char({left},'DD'),1,1) = '0' then substr(to_char({left},'DD'),2,1) else to_char({left},'DD') end || to_char({left},'";
+                                case "H": return $"') || case when substr(to_char({left},'HH24'),1,1) = '0' then substr(to_char({left},'HH24'),2,1) else to_char({left},'HH24') end || to_char({left},'";
+                                case "h": return $"') || case when substr(to_char({left},'HH12'),1,1) = '0' then substr(to_char({left},'HH12'),2,1) else to_char({left},'HH12') end || to_char({left},'";
+                                case "m": return $"') || case when substr(to_char({left},'MI'),1,1) = '0' then substr(to_char({left},'MI'),2,1) else to_char({left},'MI') end || to_char({left},'";
+                                case "s": return $"') || case when substr(to_char({left},'SS'),1,1) = '0' then substr(to_char({left},'SS'),2,1) else to_char({left},'SS') end || to_char({left},'";
+                                case "t": return $"') || rtrim(to_char({left},'AM'),'M') || to_char({left},'";
+                            }
+                            return m.Groups[0].Value;
+                        }).Replace("%_a1", "MM").Replace("%_a2", "DD").Replace("%_a3", "HH24").Replace("%_a4", "HH12").Replace("%_a5", "MI").Replace("%_a6", "AM");
+                        return isMatched == false ? $"to_char({left},{args1})" : $"(to_char({left},{args1}))".Replace($"to_char({left},'')", "''");
                 }
             }
             return null;
diff --git a/Providers/FreeSql.Provider.PostgreSQL/PostgreSQLExpression.cs b/Providers/FreeSql.Provider.PostgreSQL/PostgreSQLExpression.cs
index 157606eb..6c56f6a2 100644
--- a/Providers/FreeSql.Provider.PostgreSQL/PostgreSQLExpression.cs
+++ b/Providers/FreeSql.Provider.PostgreSQL/PostgreSQLExpression.cs
@@ -1,5 +1,4 @@
 using FreeSql.Internal;
-using FreeSql.Internal.Model;
 using Newtonsoft.Json.Linq;
 using System;
 using System.Collections;
@@ -516,7 +515,7 @@ namespace FreeSql.PostgreSQL
                     case "Equals": return $"({left} = ({args1})::timestamp)";
                     case "CompareTo": return $"extract(epoch from ({left})::timestamp-({args1})::timestamp)";
                     case "ToString":
-                        left = $"({left})::timestamp";
+                        if (left.EndsWith("::timestamp") == false) left = $"({left})::timestamp";
                         if (exp.Arguments.Count == 0) return $"to_char({left},'YYYY-MM-DD HH24:MI:SS.US')";
                         switch (args1)
                         {
diff --git a/Providers/FreeSql.Provider.SqlServer/SqlServerExpression.cs b/Providers/FreeSql.Provider.SqlServer/SqlServerExpression.cs
index 573b13fd..a657b039 100644
--- a/Providers/FreeSql.Provider.SqlServer/SqlServerExpression.cs
+++ b/Providers/FreeSql.Provider.SqlServer/SqlServerExpression.cs
@@ -374,7 +374,7 @@ namespace FreeSql.SqlServer
                     case "Equals": return $"({left} = {args1})";
                     case "CompareTo": return $"datediff(second,{args1},{left})";
                     case "ToString":
-                        left = $"cast({left} as datetime)";
+                        if (left.EndsWith(" as datetime)") == false) left = $"cast({left} as datetime)";
                         if (exp.Arguments.Count == 0) return $"convert(varchar, {left}, 121)";
                         switch (args1.TrimStart('N'))
                         {
diff --git a/Providers/FreeSql.Provider.Sqlite/SqliteExpression.cs b/Providers/FreeSql.Provider.Sqlite/SqliteExpression.cs
index 5c1ab0fa..2fb321ea 100644
--- a/Providers/FreeSql.Provider.Sqlite/SqliteExpression.cs
+++ b/Providers/FreeSql.Provider.Sqlite/SqliteExpression.cs
@@ -1,8 +1,6 @@
 using FreeSql.Internal;
-using FreeSql.Internal.Model;
 using System;
 using System.Collections;
-using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Text;