diff --git a/src/main/java/com/alibaba/druid/sql/ast/statement/NullConstraint.java b/src/main/java/com/alibaba/druid/sql/ast/statement/NullConstraint.java
new file mode 100644
index 0000000000..e55329a13c
--- /dev/null
+++ b/src/main/java/com/alibaba/druid/sql/ast/statement/NullConstraint.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright 1999-2101 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.druid.sql.ast.statement;
+
+import com.alibaba.druid.sql.visitor.SQLASTVisitor;
+
+public class NullConstraint extends SQLConstraintImpl implements SQLColumnConstraint {
+
+    public NullConstraint(){
+    }
+
+    @Override
+    protected void accept0(SQLASTVisitor visitor) {
+        visitor.visit(this);
+        visitor.endVisit(this);
+    }
+}
diff --git a/src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java b/src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java
index aae45f4a2b..883b0595d3 100644
--- a/src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java
+++ b/src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java
@@ -65,6 +65,7 @@ import com.alibaba.druid.sql.ast.expr.SQLUnaryExpr;
 import com.alibaba.druid.sql.ast.expr.SQLUnaryOperator;
 import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
 import com.alibaba.druid.sql.ast.statement.NotNullConstraint;
+import com.alibaba.druid.sql.ast.statement.NullConstraint;
 import com.alibaba.druid.sql.ast.statement.SQLAssignItem;
 import com.alibaba.druid.sql.ast.statement.SQLCharacterDataType;
 import com.alibaba.druid.sql.ast.statement.SQLCheck;
@@ -1688,7 +1689,7 @@ public class SQLExprParser extends SQLParser {
 
         if (lexer.token() == Token.NULL) {
             lexer.nextToken();
-            column.setDefaultExpr(new SQLNullExpr());
+            column.getConstraints().add(new NullConstraint());
             return parseColumnRest(column);
         }
 
diff --git a/src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java b/src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java
index 4c0781932e..39b0841064 100644
--- a/src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java
+++ b/src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java
@@ -1192,6 +1192,16 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter implements Printab
         return false;
     }
 
+    public boolean visit(NullConstraint x) {
+    	if (x.getName() != null) {
+    		print0(ucase ? "CONSTRAINT " : "constraint ");
+    		x.getName().accept(this);
+    		print(' ');
+    	}
+    	print0(ucase ? "NULL" : "null");
+    	return false;
+    }
+
     @Override
     public boolean visit(SQLUnionQuery x) {
         x.getLeft().accept(this);
diff --git a/src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitor.java b/src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitor.java
index 0f641957e7..61df27ff28 100644
--- a/src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitor.java
+++ b/src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitor.java
@@ -716,4 +716,9 @@ public interface SQLASTVisitor {
     boolean visit(SQLErrorLoggingClause x);
 
     void endVisit(SQLErrorLoggingClause x);
+
+    boolean visit(NullConstraint x);
+
+    void endVisit(NullConstraint x);
+
 }
diff --git a/src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitorAdapter.java b/src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitorAdapter.java
index fb20641240..182962c8df 100644
--- a/src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitorAdapter.java
+++ b/src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitorAdapter.java
@@ -1565,4 +1565,13 @@ public class SQLASTVisitorAdapter implements SQLASTVisitor {
     public void endVisit(SQLErrorLoggingClause x) {
 
     }
+
+    @Override
+    public boolean visit(NullConstraint x) {
+	return true;
+    }
+
+    @Override
+    public void endVisit(NullConstraint x) {
+    }
 }