diff --git a/README.md b/README.md
index fb1e715..091722e 100644
--- a/README.md
+++ b/README.md
@@ -223,6 +223,13 @@ DROP TABLE my_table IF EXISTS
 - File name can also be absolute path.
 - See `data/q1.sql` for more information 
 
+## Combine Queries
+- `UNION ALL` is a bag union of two query results with same schema. e.g. 
+```
+SELECT * FROM table 1 UNION ALL SELECT * FROM table 2
+```
+- `EXCEPT` clause will return the difference of two query results. e.g.
+  
 ## Delete Data:
 - Use a query like `DELETE FROM <table_name> [WHERE <conditions>]` to delete rows from a table that matches the conditions.
   
diff --git a/aquery_config.py b/aquery_config.py
index 0327d06..f0e64a9 100644
--- a/aquery_config.py
+++ b/aquery_config.py
@@ -2,7 +2,7 @@
 
 ## GLOBAL CONFIGURATION FLAGS
 
-version_string = '0.5.1a'
+version_string = '0.5.2a'
 add_path_to_ldpath = True
 rebuild_backend = False
 run_backend = True