DataZulu

Ah, the joys of testing Microsoft installations…

We recently got corrupted installs and an unstartable service after upgrading from SQL Server 2008 SP1 to the R2 release. The service itself wasn’t started after the upgrade completed and attempting to start it resulted in these errors in the Windows event log:

Script level upgrade for database 'master' failed because upgrade step 'sqlagent100_msdb_upgrade.sql' encountered error 598, state 1, severity 25. This is a serious error condition which might interfere with regular operation and the database will be taken offline. If the error happened during upgrade of the 'master' database, it will prevent the entire SQL Server instance from starting. Examine the previous errorlog entries for errors, take the appropriate corrective actions and re-start the database so that the script upgrade steps run to completion.

And

Cannot recover the master database. SQL Server is unable to run. Restore master from a full backup, repair it, or rebuild it. For more information about how to rebuild the master database, see SQL Server Books Online.

Both with the ever so helpful link to http://go.microsoft.com/fwlink/events.asp, possibly the most useless link on the entire interweb.

Calling upon Lord Google to help turned up lots of red herrings, mostly about cases where people have renamed the SA built in account. These didn’t apply to our situation.

Searching for “sqlagent100_msdb_upgrade 598” turned up (as of this morning) only about 3 hits, none in English. The powers of Google again rescued with a translation of this page from Portuguese to English for me.

The Problem…

Turns out one of the upgrade scripts will fail to run if the default data directory set for the SQL Instance doesn’t actually exist at the time of upgrade.

What the …?

How could you get into this predicament? you may ask.

Easy:

1. Specify a specific default data folder during the previous installation.
2. Have this be different than where SQL Server puts its own databases.
3. Never actually use it.

#3 is easy especially if you code explicit paths for your user databases when you create them, a good practice for production work.

With this recipe, the default data folder never gets created.

Along comes the magic of SQL Server 2008 R2’s upgrade logic which doesn’t bother checking if the folder exists. At some point during the upgrade it tries writing to this folder and … predictably fails.

Miserably.

It leaves SQL unable to run and the upgrade in a partial state. Even attempting to start the service like this “net start MSSQLSERVER /f /T3608” so it skips the upgrade scripts doesn’t put it in a responsive state. Hosification.

The Solution…

Easy. Find where it thinks this directory is and create it prior to starting the upgrade.

In SSMS, go to the Server node, right-click, select Properties. In the Properties dialog select the “Database Settings” page and look for the “Database default locations” near the bottom.

Or, run this script:

Then create that data directory and the upgrade should work.

Also Note: I found you can create the directory also after a failed upgrade. The next time the Service starts it will complete the previously failed scripts and be back and running.

MS SQL Server mssql, administration

As part of allowing users to connect to SQL Server remotely we often need to enable TCP/IP connections which are off by default in Express and other scenarios. While it’s simple to use SQL Server’s “Configuration Manager” to enable or disable certain protocols, sometimes we need to do things in a script, such as for an installer.

This solution uses the SQL PowerShell which is installed automatically with SQL Server 2008. I show how to do it directly or from a wrapper script such as VBScript or DOS.

Enabling TCP/IP through PowerShell

The basic PowerShell (“PS”) commands for doing this are:

Where “instance-name” is the name of the SQL Server instance to make this adjustment for.

This can be used to set up other protocols too, like Named Pipes by making the appropriate changes to the $ProtocolUri variable. Google around for these commands for the proper syntax.

Scripting the Change

The real challenge I ran into using this was that it needed to be run from a DOS batch file, not directly from within PowerShell.

Step #1 – invoking a PowerShell script from the command line.

Turns out powershell.exe expects the next text to be actual PS commands, not filenames such as for scripts. So to invoke the executable and have it execute a saved script, you need to use syntax like this:

• “&” tells it the filename may contain spaces.
• -noexit tells PowerShell not to exit without running the commands in the next file. (Intuitive, I know.)

Of course you can do this through normal VBScript shell commands and other techniques as well:

If you want commands like this to invoke with annoying users, check out Scott Hanselman’s blog entry on using a third-party utility library for running scripts in hidden windows.

Step #2 – running from DOS.

What I really wanted was a single line that could be run from within a DOS style batch file without referencing separate scripts. Turns out, we can.

• Multiple PS commands can be combined in one line, separated with semi-colons (;).
• We use single quote marks (') instead of doubles because the whole command needs to be a single argument to the PowerShell.exe invocation. In the case of nested quotes, escape the singles with 2-single quotes (''). Yeah, this can get a bit messy.

Here’s the first 5-line PowerShell script invoked by a single command from DOS. (This is all one line.)

Voila.

MS SQL Server sql, scm

The presentation given yesterday at SQL Saturday Portland is up on the download page. Or directly at this link.

MS SQL Server, Database Design, Presentations presentation, code-sample, xml, relational

So it turns out table-valued parameters can be optional with no problem. But it’s non-standard syntax. Normally, you’d have this:

The "= null" tells us it’s optional.

With table-valued ones, you have to specify “readonly” in any case (not related to optionality) and they are always also optional ... without specifying "= null". Like this:

This works and the @TblValParam does not have to be referenced during the call. It seems, conceptually, that the “table value” is always implicitly there, but if not passed in will just contain zero rows. You can still "select *" from it and get the header. Makes sense.

Treating it like a normal parameter, like this:

... gets you this fun error:

   Operand type clash: void type is incompatible with MyTableType

Fun.

I love when Microsoft products are internally inconsistent. (And by "love" I mean “hate with a passion.”)

MS SQL Server tsql

What fun it was presenting at SQL Saturday #5. Officially the first time I've presented at a technical conference. We had a great turnout and the event planners did a great job putting the whole thing together. Thanks to those who attended and for the great questions you asked!

Grab the slides and code for the presentation here.

(If link broken, just navigate over to the download page.)

MS SQL Server, Database Design, Presentations presentation, code-sample, xml, relational

(Using Visual Studio Team Suite edition for Database Professionals. A.k.a. “data-dude” because someone at Microsoft forgot to drink their creative juice that morning.)

Although I enjoy the unit-testing features of Visual Studio "Database Professional" edition (or whatever they're calling it these days), it is a ghastly oversight that you can't easily test for a procedure producing a specific expected error result.

Instead, if the database code itself experiences an error, the whole test blows chunks—that is, it fails. No matter if it got exactly the error you expected it to. I concede it's (all too) common to have little/poor/no error handling in stored procedures—but come on Microsoft! Let's encourage better practices.

I would expect to have one of the "Test Conditions" be for checking that a specific error code was produced. This would be about the 2nd most useful one (after checking for a Scalar value, which handles just about everything anyway).

(Yeah, I know, it's "extensible" and I'm free to spend a bunch of time developing my own Test Condition and plugging in it and sharing that code with everyone on the planet. But seriously? Who buys this latest MS excuse for not thinking about how to build what the community needs in the first place?)

<sigh>

So an aha! moment hit the other night which led me to this simple workaround. Let's use the trusty Scalar Value test condition combined with a TRY/CATCH block within the SQL code to test itself. Like this:

Then, we just wire up a Scalar Value to test the 1st column / 1st row for the specific Error Number you expect this to generate.

(Don't get me started on using ordinal row/column numbers for this—wow, MS has completely lost sight of what relational DBs are supposed to be!)

On my current project, we're returning a specifically formatted XML string from database procedure errors, which include a number of fixed attributes we then parse on the client. Works great. But it has a side effect of all custom-raised errors being #50000. So in this case I'm using a slightly more complex way of testing for expected errors in the CATCH part:

Happy error hunting!

Software Engineering, MS SQL Server devstudio, tsql

Okay, I'm a bit slow on the uptake. It took the SQLServerCentral.com question of the day to point this out to me...

Apparently MS made the values "true" and "false" implicitly convertible to BIT (as 1 and 0 respectively) starting with SQL 2005. For many years I've defined variables in stored procedure scripts that emulate the constants TRUE and FALSE... Something like this:

But now, instead, I can just directly reference 'true' or 'false' where necessary, such as in a where clause. For example:

Or, more plainly:


Of course, this isn't true Boolean type support. And don't get me started on the truly relational equivalents of TRUE and FALSE. But at least it's a step closer. Certainly less typing.

Also note: it does not work to convert directly to INT types though, only the BIT type. Even though BITs are theoretically a sub-type of the general Integer variable class.

MS SQL Server tsql

[Minor updates 2009-07-16 during re-posting.]

It seems developers coming from a “compiled code” background into database management struggle at first with how to version-control the database artifacts. Turns out, it isn’t really that much different. The first step is to reframe the question: “How do I version control the scripts that create my database?”

Since my good friend Chris recently asked me to remind him how we did it at a company where we worked together, I thought I’d write up a poor-man’s starter way of doing source control for database development. This works no matter what development tool or source-control system you use.

First, organize your source files:

• One file for bootstrapping. This includes "create database" and any other necessary artifacts like filegroups, custom roles, etc.
• One file per “object” like procedures, views, triggers, functions. Anything you’d want to have an independent log of changes on. For me this is usually everything except "schema" changes, by which I mean Tables with their associated constraints and indexes.
• One file per "schema version update." I tend to roll together any table/index updates with whatever DML is needed to transform and move the data into the new schema. I keep a "Version" table in the database itself (created during bootstrap) that can track these updates.
• Then, once per version update, create a little *.bat or *.vbs file that combines the necessary files in the right order for deployment.

This general strategy has worked well regardless of the source-control system I'm using.

(Aside: I recently started a little .NET utility to make this pattern easier to apply; it relies an a single XML manifest file listing the scripts in dependency order each with an attribute of which 'version' they were last modified in. The DB has a 'version' table, and provides a 2-proc interface for "GetCurrentVersion" and "UpdateVersion", then the *.exe can determine which scripts to run in which order. Updating objects in source is relatively painless because they can be checked in (n) times during iterations and the manifest is only updated when I'm confident enough in it to include in the official build/release/rollout.)

If you use the full Team Suite editions of Visual Studio, I'd also recommend Visual Studio for Database Professionals, which automates shredding the DB structure into a script&local-only environment for editing and builds deployment scripts for you. My only gripes with it are (a) it obviously doesn't handle any custom data transforms you might need during a schema update; (b) it shreds the DB a bit too granularly for my tastes -- each column, each index, each constraint, etc.

Some general tips for painless source-control:

• Make scripts "rerunnable". For DDL, I always use some variation of "if not exists... then /* do something */". For objects like procedures and triggers I use the pattern "if not exists, create <some-stub-object>; ... alter <real-object-code>". This emulates Oracle's "create or replace package" syntax which I always liked. The script works the very first time and is re-runnable.
• Include copious "print" statements for easily seeing what happened or logging your rollout to a file.
• At the top of files, include a statement that raises a severe error if you're connected to Master or something. Like this:

• Create ad hoc batch files to apply handfuls of updates as needed during development. This especially helps coordinate with other developers during tight iterations where you don't want the "real build" to see the changes yet.
• Use CodeSmith or some other tool to code-generate most of the cute little change-script stubs. I plug in TableName, ColumnName and Index Options, and get a nice little rollout script.

Some DB source-control anti-patterns:

• Don’t deploy new databases by (a) restoring a backup or (b) attaching a whole DB set of files. Ick. You lose the ability to track edits over time and you bloat your source control immensely!
• Don’t combine all schema and object changes into one huge monolithic script to update the version. You might have checkin history on that one file, but every change ever is in one file (needle in haystack problem—good luck finding the version when you messed up the tax-calculation logic!) and multiple developers working together is messy or impossible.
• Don’t develop against a 'live' database then using some—hopefully robust—third party tool to magically figure out your changes for you. I've never seen this lazy approach work robustly. Usually more time is spent validating the changes than it would have taken to just write the change scripts by hand.

I hope to post more in the future on this, including some sample files. I'm interested to hear your thoughts on what works well for you.

Database, MS SQL Server mssql, scm