From 6607cb4222794640a06bc91cb1c351755e6c69e8 Mon Sep 17 00:00:00 2001
From: Jean Praloran <jeanpralo@gmail.com>
Date: Fri, 23 Aug 2019 11:50:39 +1200
Subject: [PATCH] add support for sub-query,
 https://github.com/sdispater/orator/pull/309

---
 orator/query/builder.py | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/orator/query/builder.py b/orator/query/builder.py
index 6e8aaa6c..9c7e2e59 100644
--- a/orator/query/builder.py
+++ b/orator/query/builder.py
@@ -63,7 +63,7 @@ def __init__(self, connection, grammar, processor):
         self._processor = processor
         self._connection = connection
         self._bindings = OrderedDict()
-        for type in ["select", "join", "where", "having", "order"]:
+        for type in ["select", "from", "join", "where", "having", "order"]:
             self._bindings[type] = []
 
         self.aggregate_ = None
@@ -188,8 +188,31 @@ def from_(self, table):
         :return: The current QueryBuilder instance
         :rtype: QueryBuilder
         """
+        self.set_bindings([], "from")
         self.from__ = table
+        return self
+
+    def from_sub(self, query, as_):
+        """
+        Set the query target table to a subquery
+
+        :param query: The QueryBuilder to set as from expression
+        :type query: QueryBuilder
+
+        :param as_: The alias name for the subquery
+        :type as_: str
+
+        :return: The current QueryBuilder instance
+        :rtype: QueryBuilder
+        """
+        if not isinstance(query, QueryBuilder):
+            raise ArgumentError("From expression must be a QueryBuilder")
+
+        bindings = query.get_bindings()
+        query = "(%s) AS %s" % (query.to_sql(), self._grammar.wrap(as_))
 
+        self.set_bindings(bindings, "from")
+        self.from__ = QueryExpression(query)
         return self
 
     def join(self, table, one=None, operator=None, two=None, type="inner", where=False):