fix: Support empty insert.

queries.py

@@ -444,11 +444,14 @@ class Insert(ExtraMixin, TableQuery[QueryResult]):
 
         # TODO: Check efficiency of inserting multiple values like this
         # Also implement a Copy query
-        base = sql.SQL("INSERT INTO {table} ({columns}) VALUES {values_str}").format(
-            table=self.tableid,
-            columns=columns,
-            values_str=values_str
-        )
+        if self._columns:
+            base = sql.SQL("INSERT INTO {table} ({columns}) VALUES {values_str}").format(
+                table=self.tableid,
+                columns=columns,
+                values_str=values_str
+            )
+        else:
+            base = sql.SQL("INSERT INTO {table} DEFAULT VALUES").format(table=self.tableid)
 
         sections = [
             RawExpr(base, tuple(chain(*self._values))),