implement tuple-slices from .c collections

Added new syntax to the ``.c`` collection on all :class:`.FromClause`
objects allowing tuples of keys to be passed to ``__getitem__()``, along
with support for ``select()`` handling of ``.c`` collections directly,
allowing the syntax ``select(table.c['a', 'b', 'c'])`` to be possible. The
sub-collection returned is itself a :class:`.ColumnCollection` which is
also directly consumable by :func:`_sql.select` and similar now.

Fixes: #8285
Change-Id: I2236662c477ffc50af079310589e213323c960d1

1 files changed, 13 insertions, 0 deletions

diff --git a/doc/build/tutorial/data_select.rst b/doc/build/tutorial/data_select.rst
index 6d52b4627..b55113fd3 100644
--- a/doc/build/tutorial/data_select.rst
+++ b/doc/build/tutorial/data_select.rst
@@ -95,6 +95,7 @@ elements within each row:
 
 The following sections will discuss the SELECT construct in more detail.
 
+.. _tutorial_selecting_columns:
 
 Setting the COLUMNS and FROM clause
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -120,6 +121,18 @@ are represented by those columns::
     {opensql}SELECT user_account.name, user_account.fullname
     FROM user_account
 
+Alternatively, when using the :attr:`.FromClause.c` collection of any
+:class:`.FromClause` such as :class:`.Table`, multiple columns may be specified
+for a :func:`_sql.select` by using a tuple of string names::
+
+    >>> print(select(user_table.c['name', 'fullname']))
+    {opensql}SELECT user_account.name, user_account.fullname
+    FROM user_account
+
+.. versionadded:: 2.0 Added tuple-accessor capability to the
+   :attr`.FromClause.c` collection
+
+
 .. _tutorial_selecting_orm_entities:
 
 Selecting ORM Entities and Columns