improve

Author: digoal

201711/20171129_01.md

@@ -142,6 +142,9 @@ WINDOW two_days AS (ORDER BY date ASC ROWS 1 PRECEDING);
 ```  
 
 ## 窗口、帧 语法  
+帧，指定记录范围，如果只指定了开始，则开始记录到当前记录表示一帧，统计基于这个窗口的话，就是基于这个帧的范围数据进行统计。   
+  
+窗口，指整个窗口(over partition)范围进行统计。   
 
 A window function call represents the application of an aggregate-like function over some portion of   
 the rows selected by a query.