Re: 'text' is gone? - Mailing list pgsql-general

On Tuesday 10 February 2009 07:22:45 pm Tom Lane wrote:
> I don't think I believe the OP's premise anyway.  The concept that every
> string column has to have a specific hard-coded maximum length is an
> evil hangover from the days of punched cards.  It seems very unlikely
> that M$, who are not exactly known for slavish adherence to standards to
> begin with, would suddenly drop a more flexible datatype and make all
> their customers use a less flexible one.
>
> I'd be *much* less surprised to see 'text' or some moral equivalent of
> it (such as our varchar-without-length) show up in a future SQL spec
> than to see any major implementation remove it.
>
>                         regards, tom lane

I have been reading in several emails, blog, and other posts that data
type 'text' has been deprecated.  The premise may be wrong but that's what I
have been reading.  "deprecated" normally mean dropped in the future.  From
the answers I received it looks like they are following Postgres varchar().
Please see the link and the description of varchar(max).

http://www.sitecrafting.com/blog/ms-sql-server/

Please check the title - MS SQL Server 2005 text and ntext dated Oct 2008.
Which is just one I have read.

Below is a discription of the replacement.

 Understanding VARCHAR(MAX) in SQL Server 2005In SQL Server 2000 and SQL
Server 7, a row cannot exceed 8000 bytes in size. This means that a VARBINARY
column can only store 8000 bytes (assuming it is the only column in a table),
a VARCHAR column can store up to 8000 characters and an NVARCHAR column can
store up to 4000 characters (2 bytes per unicode character). This limitation
stems from the 8 KB internal page size SQL Server uses to save data to disk.

To store more data in a single column, you needed to use the TEXT, NTEXT, or
IMAGE data types (BLOBs) which are stored in a collection of 8 KB data pages
that are separate from the data pages that store the other data in the same
table. These data pages are arranged in a B-tree structure. BLOBs are hard to
work with and manipulate. They cannot be used as variables in a procedure or
a function and they cannot be used inside string functions such as REPLACE,
CHARINDEX or SUBSTRING. In most cases, you have to use READTEXT, WRITETEXT,
and UPDATETEXT commands to manipulate BLOBs.

To solve this problem, Microsoft introduced the VARCHAR(MAX),  NVARCHAR(MAX),
and VARBINARY(MAX) data types in SQL Server 2005. These data types can hold
the same amount of data BLOBs can hold (2 GB) and they are stored in the same
type of data pages used for other data types. When data in a MAX data type
exceeds 8 KB, an over-flow page is used. SQL Server 2005 automatically
assigns an over-flow indicator to the page and knows how to manipulate data
rows the same way it manipulates other data types. You can declare variables
of MAX data types inside a stored procedure or function and even pass them as
variables. You can also use them inside string functions.

Microsoft recommend using MAX data types instead of BLOBs in SQL Server 2005.
In fact, BLOBs are being deprecated in future releases of SQL Server.



--
John Fabiani