Add support for "real" sequences in mssql

Added support for "CREATE SEQUENCE" and full :class:`.Sequence` support for
Microsoft SQL Server.  This removes the deprecated feature of using
:class:`.Sequence` objects to manipulate IDENTITY characteristics which
should now be performed using ``mssql_identity_start`` and
``mssql_identity_increment`` as documented at :ref:`mssql_identity`. The
change includes a new parameter :paramref:`.Sequence.data_type` to
accommodate SQL Server's choice of datatype, which for that backend
includes INTEGER and BIGINT.   The default starting value for SQL Server's
version of :class:`.Sequence` has been set at 1; this default is now
emitted within the CREATE SEQUENCE DDL for all backends.

Fixes: #4235
Fixes: #4633
Change-Id: I6aa55c441e8146c2f002e2e201a7f645e667b916

2 files changed, 46 insertions, 1 deletions

diff --git a/doc/build/changelog/migration_14.rst b/doc/build/changelog/migration_14.rst
index 9c7d5fa55..6702f86f0 100644
--- a/doc/build/changelog/migration_14.rst
+++ b/doc/build/changelog/migration_14.rst
@@ -1599,4 +1599,31 @@ was not created.
 
     :ref:`defaults_sequences`
 
-:ticket:`4976`
\ No newline at end of file
+:ticket:`4976`
+
+
+.. _change_4235:
+
+Added Sequence support distinct from IDENTITY to SQL Server
+-----------------------------------------------------------
+
+The :class:`.Sequence` construct is now fully functional with Microsoft
+SQL Server.  When applied to a :class:`.Column`, the DDL for the table will
+no longer include IDENTITY keywords and instead will rely upon "CREATE SEQUENCE"
+to ensure a sequence is present which will then be used for INSERT statements
+on the table.
+
+The :class:`.Sequence` prior to version 1.3 was used to control parameters for
+the IDENTITY column in SQL Server; this usage emitted deprecation warnings
+throughout 1.3 and is now removed in 1.4.  For control of paramters for an
+IDENTITY column, the ``mssql_identity_start`` and ``mssql_identity_increment``
+parameters should be used; see the MSSQL dialect documentation linked below.
+
+
+.. seealso::
+
+    :ref:`mssql_identity`
+
+:ticket:`4235`
+
+:ticket:`4633`
diff --git a/doc/build/changelog/unreleased_14/4235.rst b/doc/build/changelog/unreleased_14/4235.rst
new file mode 100644
index 000000000..acd1ff1ce
--- /dev/null
+++ b/doc/build/changelog/unreleased_14/4235.rst
@@ -0,0 +1,18 @@
+.. change::
+    :tags: sql, mssql
+    :tickets: 4235, 4633
+
+    Added support for "CREATE SEQUENCE" and full :class:`.Sequence` support for
+    Microsoft SQL Server.  This removes the deprecated feature of using
+    :class:`.Sequence` objects to manipulate IDENTITY characteristics which
+    should now be performed using ``mssql_identity_start`` and
+    ``mssql_identity_increment`` as documented at :ref:`mssql_identity`. The
+    change includes a new parameter :paramref:`.Sequence.data_type` to
+    accommodate SQL Server's choice of datatype, which for that backend
+    includes INTEGER, BIGINT, and DECIMAL(n, 0).   The default starting value
+    for SQL Server's version of :class:`.Sequence` has been set at 1; this
+    default is now emitted within the CREATE SEQUENCE DDL for all backends.
+
+    .. seealso::
+
+        :ref:`change_4235`
\ No newline at end of file