bug fixed for exprList

src/main/java/com/alibaba/druid/sql/ast/SQLOrderBy.java

@@ -74,4 +74,5 @@ public class SQLOrderBy extends SQLObjectImpl {
         return true;
     }
 
+
 }

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;
     }

src/main/java/com/alibaba/druid/sql/ast/statement/SQLSelectOrderByItem.java

@@ -25,6 +25,7 @@ public class SQLSelectOrderByItem extends SQLObjectImpl {
     protected SQLExpr                  expr;
     protected String                   collate;
     protected SQLOrderingSpecification type;
+    protected NullsOrderType             nullsOrderType;
 
     public SQLSelectOrderByItem(){
 
@@ -60,6 +61,14 @@ public class SQLSelectOrderByItem extends SQLObjectImpl {
     public void setType(SQLOrderingSpecification type) {
         this.type = type;
     }
+    
+    public NullsOrderType getNullsOrderType() {
+        return this.nullsOrderType;
+    }
+
+    public void setNullsOrderType(NullsOrderType nullsOrderType) {
+        this.nullsOrderType = nullsOrderType;
+    }
 
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor.visit(this)) {
@@ -95,4 +104,19 @@ public class SQLSelectOrderByItem extends SQLObjectImpl {
         return true;
     }
 
+    public static enum NullsOrderType {
+        NullsFirst, NullsLast;
+
+        public String toFormalString() {
+            if (NullsFirst.equals(this)) {
+                return "NULLS FIRST";
+            }
+
+            if (NullsLast.equals(this)) {
+                return "NULLS LAST";
+            }
+
+            throw new IllegalArgumentException();
+        }
+    }
 }