Merge branch 'master' of https://github.com/sunyinqi0508/AQuery2

README.md

@@ -223,6 +223,9 @@ DROP TABLE my_table IF EXISTS
 - File name can also be absolute path.
 - See `data/q1.sql` for more information 
 
+## Delete Data:
+- Use a query like `DELETE FROM <table_name> [WHERE <conditions>]` to delete rows from a table that matches the conditions.
+  
 ## Built-in functions: 
 - `avg[s]`: average of a column. `avgs(col), avgs(w, col)` is rolling and moving average with window `w` of the column `col`.
 - `var[s]`, `stddev[s]`: [moving/rolling] **population** variance, standard deviation.

reconstruct/ast.py

@@ -937,7 +937,8 @@ class filter(ast_node):
     def produce(self, node):
         filter_expr = expr(self, node)
         self.add(filter_expr.sql)
-        self.datasource.join_conditions += filter_expr.join_conditions
+        if self.datasource is not None:
+            self.datasource.join_conditions += filter_expr.join_conditions
         
 class create_table(ast_node):
     name = 'create_table'
@@ -1052,7 +1053,19 @@ class insert(ast_node):
             
         self.sql += ', '.join(list_values) 
         
-  
+
+class delete_table(ast_node):
+    name = 'delete'
+    first_order = name
+    def init(self, node):
+        super().init(node)
+            
+    def produce(self, node):
+        tbl = node['delete']
+        self.sql = f'DELETE FROM {tbl} '
+        if 'where' in node:
+            self.sql += filter(self, node['where']).sql
+
 class load(ast_node):
     name="load"
     first_order = name