improve sql parser

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

@@ -15,6 +15,7 @@
  */
 package com.alibaba.druid.sql.dialect.mysql.parser;
 
+import com.alibaba.druid.sql.ast.SQLDataType;
 import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLName;
 import com.alibaba.druid.sql.ast.expr.SQLBinaryOpExpr;
@@ -555,6 +556,17 @@ public class MySqlExprParser extends SQLExprParser {
 
         return column;
     }
+    
+    protected SQLDataType parseDataTypeRest(SQLDataType dataType) {
+        super.parseDataTypeRest(dataType);
+        
+        if (identifierEquals("UNSIGNED")) {
+            lexer.nextToken();
+            dataType.getAttributes().put("unsigned", true);
+        }
+
+        return dataType;
+    }
 
     public SQLExpr orRest(SQLExpr expr) {
 

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

@@ -326,6 +326,10 @@ public class MySqlOutputVisitor extends SQLASTOutputVisitor implements MySqlASTV
             printAndAccept(x.getArguments(), ", ");
             print(")");
         }
+        
+        if (Boolean.TRUE == x.getAttribute("unsigned")) {
+            print(" unsigned");
+        }
 
         if (x instanceof SQLCharactorDataType) {
             SQLCharactorDataType charType = (SQLCharactorDataType) x;