Wanted: Automatic Columns

Louis Davidson plucks an old Connect item out for a new look:

The concept is very similar to a DEFAULT constraint, with two differences:

1. Will work on an UPDATE operation, without specifying DEFAULT

2. Could be configured to disallow the user from entering a value. My proposed syntax was pretty simple:

AUTO [WITH OVERRIDE] (scalar expression)

Now I realize that 10 years ago, I didn’t take terribly long to consider that WITH was a terrible thing to add to the syntax, and AUTO is a keyword already, so I am going to rename it: AUTO_DEFAULT (scalar expression, [option]). Since I have thought a bit more about this in the years since writing it, I realized there were a few more options that would be nice. I was terrible in college doing syntax parsing, but the syntax itself is not important. Temporal in SQL Server 2016 has syntax that is similar to this for the new temporal columns which I got really excited about the first time I saw it: SysStartTime datetime2 GENERATED ALWAYS AS ROW START NOT NULL. Maybe in vNext?

Read the whole thing.  Then check out the related Connect item Adam Machanic submitted.  I’d love to see that functionality, given how frequently I create these metadata columns.

Related Posts

Comparing System Metadata Between SQL Server Versions

Aaron Bertrand shows how he finds hidden features in new SQL Server builds: One of the areas I like to focus on is new features in SQL Server. Under both MVP and Microsoft Partner programs, I get to see a lot of builds of SQL Server that don’t make it to the public, and documentation […]

Read More

The Problems With NOLOCK

Rob Farley demonstrates the downside of the READ UNCOMMITTED isolation level: I’m going to create a table and insert exactly 1 million rows. This particular table will be a clustered index, and will contain 1 million GUIDs. 1 2 CREATE TABLE dbo.demoNOLOCK (someguid uniqueidentifier NOT NULL PRIMARY KEY); INSERT dbo.demoNOLOCK (someguid) SELECT TOP (1000000) NEWID() […]

Read More


January 2017
« Dec Feb »