improve mysql ddl parser

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlSQLColumnDefinition.java

@@ -15,6 +15,7 @@
  */
 package com.alibaba.druid.sql.dialect.mysql.ast.statement;
 
+import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.statement.SQLColumnDefinition;
 
 public class MySqlSQLColumnDefinition extends SQLColumnDefinition {
@@ -23,6 +24,8 @@ public class MySqlSQLColumnDefinition extends SQLColumnDefinition {
 
     private boolean           autoIncrement    = false;
 
+    private SQLExpr           onUpdate;
+
     public MySqlSQLColumnDefinition(){
 
     }
@@ -35,4 +38,12 @@ public class MySqlSQLColumnDefinition extends SQLColumnDefinition {
         this.autoIncrement = autoIncrement;
     }
 
+    
+    public SQLExpr getOnUpdate() {
+        return onUpdate;
+    }
+    
+    public void setOnUpdate(SQLExpr onUpdate) {
+        this.onUpdate = onUpdate;
+    }
 }

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlExprParser.java

@@ -530,6 +530,13 @@ public class MySqlExprParser extends SQLExprParser {
     }
 
     public SQLColumnDefinition parseColumnRest(SQLColumnDefinition column) {
+        if (lexer.token() == Token.ON) {
+            lexer.nextToken();
+            accept(Token.UPDATE);
+            SQLExpr expr = this.expr();
+            ((MySqlSQLColumnDefinition) column).setOnUpdate(expr);
+        }
+        
         if (identifierEquals("AUTO_INCREMENT")) {
             lexer.nextToken();
             if (column instanceof MySqlSQLColumnDefinition) {

src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlOutputVisitor.java

@@ -295,7 +295,13 @@ public class MySqlOutputVisitor extends SQLASTOutputVisitor implements MySqlASTV
                 x.getDefaultExpr().accept(this);
             }
         }
-
+        
+        if (mysqlColumn != null && mysqlColumn.getOnUpdate() != null) {
+            print(" ON UPDATE ");
+            
+            mysqlColumn.getOnUpdate().accept(this);
+        }
+        
         if (mysqlColumn != null && mysqlColumn.isAutoIncrement()) {
             print(" AUTO_INCREMENT");
         }