From 1091861bb15876131653191ae409a523aa8ec0c5 Mon Sep 17 00:00:00 2001
From: Louis Xu <rdxiaolei@gmail.com>
Date: Fri, 15 Apr 2016 18:21:13 +0800
Subject: [PATCH] [bug fix] keep column name unchanged if aliasMap value is
 null

---
 .../com/alibaba/druid/sql/visitor/SchemaStatVisitor.java    | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/main/java/com/alibaba/druid/sql/visitor/SchemaStatVisitor.java b/src/main/java/com/alibaba/druid/sql/visitor/SchemaStatVisitor.java
index 9839bf9bc7..54dc56d25a 100644
--- a/src/main/java/com/alibaba/druid/sql/visitor/SchemaStatVisitor.java
+++ b/src/main/java/com/alibaba/druid/sql/visitor/SchemaStatVisitor.java
@@ -760,12 +760,14 @@ public class SchemaStatVisitor extends SQLASTVisitorAdapter {
         Map<String, String> aliasMap = getAliasMap();
 
         if (aliasMap != null) {
-            if (aliasMap.containsKey(name)) {
+            if (aliasMap.containsKey(name)
+            		&& aliasMap.get(name) != null) {
                 return aliasMap.get(name);
             }
             
             String name_lcase = name.toLowerCase();
-            if (name_lcase != name && aliasMap.containsKey(name_lcase)) {
+            if (name_lcase != name && aliasMap.containsKey(name_lcase)
+            		&& aliasMap.get(name_lcase) != null) {
                 return aliasMap.get(name_lcase);
             }