diff --git a/FreeSql.Tests/FreeSql.Tests.Provider.MySqlConnector/MySqlConnector/MySqlCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests.Provider.MySqlConnector/MySqlConnector/MySqlCodeFirstTest.cs
index 329b4e61..a00a399b 100644
--- a/FreeSql.Tests/FreeSql.Tests.Provider.MySqlConnector/MySqlConnector/MySqlCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests.Provider.MySqlConnector/MySqlConnector/MySqlCodeFirstTest.cs
@@ -21,6 +21,9 @@ namespace FreeSql.Tests.MySqlConnector
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Dameng/DamengCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Dameng/DamengCodeFirstTest.cs
index 44718c65..98e1eeea 100644
--- a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Dameng/DamengCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Dameng/DamengCodeFirstTest.cs
@@ -21,6 +21,9 @@ namespace FreeSql.Tests.Odbc.Dameng
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/MySql/MySqlCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/MySql/MySqlCodeFirstTest.cs
index d0657318..ebc6c398 100644
--- a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/MySql/MySqlCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/MySql/MySqlCodeFirstTest.cs
@@ -21,6 +21,9 @@ namespace FreeSql.Tests.Odbc.MySql
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Oracle/OracleCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Oracle/OracleCodeFirstTest.cs
index 37482571..ef9c6147 100644
--- a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Oracle/OracleCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/Oracle/OracleCodeFirstTest.cs
@@ -21,6 +21,9 @@ namespace FreeSql.Tests.Odbc.Oracle
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/PostgreSQL/PostgreSQLCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/PostgreSQL/PostgreSQLCodeFirstTest.cs
index 320146c0..179a66d8 100644
--- a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/PostgreSQL/PostgreSQLCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/PostgreSQL/PostgreSQLCodeFirstTest.cs
@@ -25,6 +25,9 @@ namespace FreeSql.Tests.Odbc.PostgreSQL
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/SqlServer/SqlServerCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/SqlServer/SqlServerCodeFirstTest.cs
index ef642d6b..1eb1d44a 100644
--- a/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/SqlServer/SqlServerCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests.Provider.Odbc/SqlServer/SqlServerCodeFirstTest.cs
@@ -23,6 +23,9 @@ namespace FreeSql.Tests.Odbc.SqlServer
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests/MsAccess/MsAccessCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests/MsAccess/MsAccessCodeFirstTest.cs
index ceeca39b..826cb13b 100644
--- a/FreeSql.Tests/FreeSql.Tests/MsAccess/MsAccessCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests/MsAccess/MsAccessCodeFirstTest.cs
@@ -21,6 +21,9 @@ namespace FreeSql.Tests.MsAccess
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests/MySql/MySqlCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests/MySql/MySqlCodeFirstTest.cs
index 1c3cd9ed..b3ccdd26 100644
--- a/FreeSql.Tests/FreeSql.Tests/MySql/MySqlCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests/MySql/MySqlCodeFirstTest.cs
@@ -21,6 +21,9 @@ namespace FreeSql.Tests.MySql
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests/Oracle/OracleCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests/Oracle/OracleCodeFirstTest.cs
index 959a9b96..8e7d09c8 100644
--- a/FreeSql.Tests/FreeSql.Tests/Oracle/OracleCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests/Oracle/OracleCodeFirstTest.cs
@@ -21,6 +21,9 @@ namespace FreeSql.Tests.Oracle
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests/PostgreSQL/PostgreSQLCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests/PostgreSQL/PostgreSQLCodeFirstTest.cs
index f131c212..700f2d6d 100644
--- a/FreeSql.Tests/FreeSql.Tests/PostgreSQL/PostgreSQLCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests/PostgreSQL/PostgreSQLCodeFirstTest.cs
@@ -28,6 +28,9 @@ namespace FreeSql.Tests.PostgreSQL
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests/SqlServer/SqlServerCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests/SqlServer/SqlServerCodeFirstTest.cs
index f3e55e01..368eddf8 100644
--- a/FreeSql.Tests/FreeSql.Tests/SqlServer/SqlServerCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests/SqlServer/SqlServerCodeFirstTest.cs
@@ -22,6 +22,9 @@ namespace FreeSql.Tests.SqlServer
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql.Tests/FreeSql.Tests/Sqlite/SqliteCodeFirstTest.cs b/FreeSql.Tests/FreeSql.Tests/Sqlite/SqliteCodeFirstTest.cs
index 12073a43..03b30986 100644
--- a/FreeSql.Tests/FreeSql.Tests/Sqlite/SqliteCodeFirstTest.cs
+++ b/FreeSql.Tests/FreeSql.Tests/Sqlite/SqliteCodeFirstTest.cs
@@ -21,6 +21,9 @@ namespace FreeSql.Tests.Sqlite
             public Guid Id { get; set; }
             [Column(StringLength = 50)]
             public string Title { get; set; }
+
+            [Column(IsNullable = false, StringLength = 50)]
+            public string TitleSub { get; set; }
         }
 
         [Fact]
diff --git a/FreeSql/Internal/UtilsExpressionTree.cs b/FreeSql/Internal/UtilsExpressionTree.cs
index ffb1dfb8..efdb4a8a 100644
--- a/FreeSql/Internal/UtilsExpressionTree.cs
+++ b/FreeSql/Internal/UtilsExpressionTree.cs
@@ -124,7 +124,7 @@ namespace FreeSql.Internal
                 if ((colattr.IsNullable != true || colattr.IsIdentity == true || colattr.IsPrimary == true) && colattr.DbType.Contains("NOT NULL") == false)
                 {
                     colattr.IsNullable = false;
-                    colattr.DbType += " NOT NULL";
+                    colattr.DbType = Regex.Replace(colattr.DbType, @"\bNULL\b", "").Trim() + " NOT NULL";
                 }
                 if (colattr.IsNullable == true && colattr.DbType.Contains("NOT NULL")) colattr.DbType = colattr.DbType.Replace("NOT NULL", "");
                 colattr.DbType = Regex.Replace(colattr.DbType, @"\([^\)]+\)", m =>