bug fixed for exprList

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

@@ -21,6 +21,7 @@ import java.util.List;
 
 import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLExprImpl;
+import com.alibaba.druid.sql.ast.SQLOrderBy;
 import com.alibaba.druid.sql.ast.SQLOver;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
@@ -31,9 +32,9 @@ public class SQLAggregateExpr extends SQLExprImpl implements Serializable {
     protected Option              option;
     protected final List<SQLExpr> arguments        = new ArrayList<SQLExpr>();
     protected SQLOver             over;
+    protected SQLOrderBy          withinGroup;
 
     public SQLAggregateExpr(String methodName){
-
         this.methodName = methodName;
     }
 
@@ -50,6 +51,18 @@ public class SQLAggregateExpr extends SQLExprImpl implements Serializable {
         this.methodName = methodName;
     }
 
+    public SQLOrderBy getWithinGroup() {
+        return withinGroup;
+    }
+
+    public void setWithinGroup(SQLOrderBy withinGroup) {
+        if (withinGroup != null) {
+            withinGroup.setParent(this);
+        }
+        
+        this.withinGroup = withinGroup;
+    }
+
     public Option getOption() {
         return this.option;
     }