改进alias方法

library/think/db/Query.php

@@ -1523,7 +1523,12 @@ class Query
     {
         if (is_array($alias)) {
             foreach ($alias as $key => $val) {
-                $this->options['alias'][$key] = $val;
+                if (false !== strpos($key, '__')) {
+                    $table = $this->parseSqlTable($key);
+                } else {
+                    $table = $key;
+                }
+                $this->options['alias'][$table] = $val;
             }
         } else {
             if (isset($this->options['table'])) {