Voice of the DBA

Category: Blog

ALTER SCHEMA TO ADD PERMISSIONS
I’m sure some of you have wanted to do this:

ALTER SCHEMA Steve AUTHORIZATION Steve

You realize this doesn’t work, and you can’t grant the user Steve, rights to his schema after it’s created. You can do this:

CREATE SCHEMA Steve Authorization Steve

UPDATE: Someone pointed out this works after the fact:

ALTER AUTHORIZATION ON SCHEMA::Steve TO Steve

But not alter it. Strange and annoying. In my last post, I showed dropping and recreating the schema. That works well if you are beginning development, but not when you’re in the middle.

Let’s make this less confusing and see how we actually allow a developer to access a schema to create procedures (or other objects) when the schema exists.

First, let’s assume we want a developer, Steve, to be able to create procedures in the ETL schema. We have these conditions:
- The ETL schema exists
- The ETL schema is owned by another developer.
- The login and user, Steve, exists in this database with no permissions.
I want to now allow Steve to build the procedure ETL.MyProc.

Grant Permissions

The first thing I do is grant create procedure permissions to Steve.

CREATE LOGIN steve WITH PASSWORD = ‘Test’;
GO
USE Sandbox
GO
CREATE USER Steve FOR LOGIN Steve
GO
GRANT CREATE PROCEDURE to Steve;

GO

With this done, now let’s set up our schema.

CREATE SCHEMA ETL
GO
There are no default permissions, so the user Steve cannot create ETL.MyProc right now. How do we fix this?

The trick here is that I need to allow Steve to ALTER the schema. I can do this by using this statement.

GRANT ALTER ON SCHEMA::ETL TO Steve;
GO

I could do other things. I could grant CONTROL. to Steve instead, but I might not want to do that. That gives Steve the ability to actually drop the schema, which probably isn’t want. It’s certainly not the “least permissions” to let the developer create objects in a schema.
March 18, 2015
Data Generator – Limiting Values

This is a series on SQL Data Generator, covering some interesting scenarios I’ve run into. If you’ve never tried it, SQL Data Generator is a part of the SQL Toolbelt. Give it a try today with an evaluation today.

I needed to generate some data for some development work on the SSC database. No, I’m not allowed to change code directly, but I was looking to send some changes to the development team, already done, and then hopefully just have them test and deploy it.

In my case, to avoid exposing any real data in case of issues, I downloaded the schema only to my laptop. The I created a database with all the objects. One of my first areas of work was on the points and scoring systems, but to do that, I needed points.

I fired up my copy of Data Generator, let it detect the objects, and pre-populate the fields and clicked “Generate Data”. That worked well, and I had a bunch of data in my system.

My first area of work was to rewrite some procedures that perform calculation. I did that, ran a simple SUM, and got this:

Msg 220, Level 16, State 2, Line 3
Arithmetic overflow error for data type int

Not what I expected. I just generated some data and ran a sum. What could be the issue?

It turns out that the default settings for integer columns are shown here:

That’s great if you want a random distribution, but it’s not so good in this case. The points values I want to store for each row should be fro 1 to 7, and randomly distributed. I’d actually like them to be weighted towards 1 and 2, but for this project, it doesn’t matter.

I decided to fix things by first deleting all the points data. Once this was done, I could then select the table on the left, and select the column.

This changes the right panel to the specific settings for this column. I changed the values, as you can see here, to be more in line with my needs. Only values from 0 to 7 are included.

I could actually use different settings for different columns. For example, for the PointsCategory column, I used these settings, from 1 to 1,000.

With these new settings, I generated new data for this table, and then my aggregate calculations worked.

Data generation is a very handy thing to have, especially in development environments where you don’t want live data. In my case, while I think my systems are fairly safe, I’d hate to lose my laptop, with a copy of the SQLServerCentral database and a million emails that people might not want shared.

March 17, 2015
The Demo Setup–Attaching Databases with Powershell
I found another use for Powershell, one actually suggested by someone else: attaching specific SQL Server databases.

TL;DR I have a script that detaches all user databases from a SQL Server instance and then reattches certain ones. Full script at the end.

The Issue

We have a lot of demo databases on our demo VMs for Red Gate. Some specific databases are used to show things with different products, but it ends up with us having a few dozen databases on an instance of SQL Server.

That’s not the best way to show things to users, as they can get confused with so many databases. Specifically for us, we have a set of databases for one of our classes, a different set for a second class, and a third set for a third class. We do this because things need to be set in different stages for each class.

One of our sales engineers said it would be great if we could hide some databases when we didn’t need them. I immediately saw a use for Powershell here.

Approach

My approach to this problem would be this.
- detach all user databases
- attach specific databases by specifying the name of the database, and the mdf/ldf/ndf file names.
- use a batch file the user can double click on the desktop to run the Powershell script.
This seemed to make sense, and I started to tackle this on one of my machines in this manner. However because I detached all my databases first, all of a sudden working on things was a pain. As a result, I setup a new VM and created dummy databases there. I first worked on the attach piece, and then the detach part.

Detaching User Databases

This was fairly simple, and I’ve written about it before. In this case, I merely cut and pasted this code into my script.

$srv = New-Object ‘Microsoft.SqlServer.Management.SMO.Server’ $instance

#detach all user databases
$dbnames = $srv.Databases.name

foreach ($dbn in $dbnames) {
    Write-Host $dbn
    if ($dbn -ne "master" -and $dbn -ne "model" -and $dbn -ne "msdb" -and $dbn -ne "tempdb") {
      $srv.DetachDatabase($dbn, $false)

      }
    }

The first line is actually needed for both parts of the script, and we re-use that object later.

The script gets a handle to the databases object and then a collection of all the names. We loop through the collection and if we aren’t looking at one of the four system databases, we call the detachDatabase method.

Note that this means I’m in control of the instance and I know I don’t have a distribution database or anything else that might break. For me, I can safely drop everything other than master/model/msdb/tempdb.

Attaching Databases

I had to search around for some example code. I guess I didn’t have to, but the docs from MS can be tricky to put together, so I searched and found a few examples. Specifically, I ran across this post that described how to attach a single database.

I decided to begin by building up the db name and paths to the files. I started by setting a variable to the path and database name.

$sqldatapath = "C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\"

$dbn = "sandbox"

One of my databases is “Sandbox” and the path for all my database files is given as the default.

Next I build up the mdf/ldf files. In my case, I don’t have anything other than single mdf file databases.

$mdffiles = $sqldatapath + $dbn + ".mdf"
write-host $mdffiles
$ldffiles = $sqldatapath + $dbn + "_Log.ldf"
write-host $ldffiles

With these, I now can tell what I’m doing. I write the data out to the host, mostly so that if something breaks, the user can determine where. We’re all technical, but it’s nice to know what’s broken.

These are the important bits, but now I need a place to store them. At only one time in the script, I create a new StringCollection object.

$dbfiles = New-Object System.Collections.Specialized.StringCollection

I’ll reuse this object for each database. In this object, I store the database file names. I use the .Add method to get them in here.

$dbfiles.Add($mdffiles)
$dbfiles.Add($ldffiles)

Now I have all my parameters. I can call the AttachDatabase method.

$srv.AttachDatabase($dbn, $dbfiles, "sa", "None")

The documentation says I need an owner, and for simplicity, I use “sa”. I also can specify options, but I don’t care in this case.

This attaches my first database. However, I need to repeat this. I could build some loop and use some array, which is probably better, but for the sake of simplicity here, and preventing issues, I copy and paste this code multiple times. In my case, I have no more than 4 databases, for any environment, so I merely copy/paste this code and change the database name.

However, I don’t want to keep adding to my StringCollection each time. In between each set of databases I need to call, I add this:

$dbfiles.Clear()

Now I have a few simple scripts I can modify easily, and others can understand them.

The Batch File

The other thing I learned with the batch file is that it doesn’t have the same context as my editing session. I had to add a line to load the SQLPS stuff at the beginning for it to work.

Import-Module "sqlps" -DisableNameChecking

I also had to ensure the execution policy is set on each machine, but we tend to do that when we set up the machines.

Simplicity

This is the simple way. It’s really not the best way, and if these scripts change much, this is a problematic way of doing things. I really should have a loop with a list of databases in one place in the script. That way if I add or remove a database, I can easily do it.

That’s an improvement I’ll make.

Let me also say that I have a pattern of database names, and files. If I needed to handle different file locations and varying numbers of files, I think this approach actually works better. Each section of the script can be edited easily, and separately, without worrying about complex logic.

I like simple.

Scripts

The batch script is this.

powershell c:\Utilities\attach_demodbs.ps1

I call the Powershell host and give a fully qualified path to the script.

Here is one of my demo scripts, for two databases: sandbox and EncryptionPrimer:

<#

Attach Demo Databases

This script detaches all user databases and then attaches the following databases

Attaches
– Sandbox
– EncryptionPrimer

#>

Import-Module "sqlps" -DisableNameChecking

$srv = New-Object ‘Microsoft.SqlServer.Management.SMO.Server’ $instance

#detach all user databases
$dbnames = $srv.Databases.name

foreach ($dbn in $dbnames) {
    Write-Host $dbn
    if ($dbn -ne "master" -and $dbn -ne "model" -and $dbn -ne "msdb" -and $dbn -ne "tempdb") {
      $srv.DetachDatabase($dbn, $false)

      }
    }

$dbfiles = New-Object System.Collections.Specialized.StringCollection

$sqldatapath = "C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\"

$dbn = "sandbox"

write-host "Instance: " $srv.Name
write-host "Attach " $dbn

$mdffiles = $sqldatapath + $dbn + ".mdf"
write-host $mdffiles
$ldffiles = $sqldatapath + $dbn + "_Log.ldf"
write-host $ldffiles

$dbfiles.Add($mdffiles)
$dbfiles.Add($ldffiles)

$srv.AttachDatabase($dbn, $dbfiles, "sa", "None")

$dbfiles.Clear()

#attach staging
$dbn = "EncryptionPrimer"

write-host "Instance: " $srv.Name
write-host "Attach " $dbn

$mdffiles = $sqldatapath + $dbn + ".mdf"
write-host "MDF: " $mdffiles
$ldffiles = $sqldatapath + $dbn + "_Log.ldf"
write-host "LDF: " $ldffiles

$dbfiles.Add($mdffiles)
$dbfiles.Add($ldffiles)

$srv.AttachDatabase($dbn, $dbfiles, "sa", "None")

$dbfiles.Clear()
March 16, 2015
Back

It’s amazing to think I’ve been gone 10 days, out of the country. SQL Bits was amazing, and still is the best SQL Server conference in the world I’ve seen. I haven’t been to them all, but this is the best of those I go to.

Ireland was fantastic, and a very warm welcome for a day of training and then a talk at the Dublin SQL Server User Group. Some really interesting questions for me to blog about and answer in the next few weeks.

I saw some neat SQL Server tips, tricks, ideas, and inspirations, which is always a good thing as it motivates me to do more and learn more as my career progresses.

And I got a new shirt:

An amazing gift from the crew at SQL Bits. My own speaker shirt. I was quite touched and I really appreciate the effort they went to. I know what I’ll be wearing next year.

A few people were jealous, since the "regular" speaker shirts were blue polos. I guess I stand out a bit from them. The Friday night party was fun, with the Captain making an appearance.

All in all a great trip.

Now back to work.

March 13, 2015