improved sql parser.

src/main/java/com/alibaba/druid/sql/ast/expr/SQLBinaryOpExpr.java

@@ -35,6 +35,8 @@ public class SQLBinaryOpExpr extends SQLExprImpl implements SQLReplaceable, Seri
     private SQLBinaryOperator operator;
     private String            dbType;
 
+    private boolean          bracket  = false;
+
     public SQLBinaryOpExpr(){
 
     }
@@ -99,6 +101,14 @@ public class SQLBinaryOpExpr extends SQLExprImpl implements SQLReplaceable, Seri
         this.operator = operator;
     }
 
+    public boolean isBracket() {
+        return bracket;
+    }
+
+    public void setBracket(boolean bracket) {
+        this.bracket = bracket;
+    }
+
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor.visit(this)) {
             acceptChild(visitor, this.left);

src/main/java/com/alibaba/druid/sql/ast/expr/SQLQueryExpr.java

@@ -87,4 +87,14 @@ public class SQLQueryExpr extends SQLExprImpl implements Serializable {
         }
         return true;
     }
+
+    public SQLQueryExpr clone() {
+        SQLQueryExpr x = new SQLQueryExpr();
+
+        if (subQuery != null) {
+            x.setSubQuery(subQuery.clone());
+        }
+
+        return x;
+    }
 }