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Applied SQL: Orphan a user, fix orphaned users (sp_FixOrphanedUsers)

olivertwistEver heard of orphaned users? It’s a database user account, disconnected from its associated login. You typically get this when you take a database backup, and restore it to a different server.

Microsoft provides us with the ever helpful sp_change_users_login to find and repair orphaned users, but even so, it’s kind of a PITA* manual operation. To simplify and provide for automation, I’ve put together the brand-spanking-new sp_FixOrphanedUsers.

First, let’s orphan some users

If you’d like to test this, here is a repro scenario that creates an orphaned user on a single instance. It orphans a user by doing the following:

  1. Create a login “OliverTwist”**.
  2. Create a database.
  3. Create a user in that database from the “OliverTwist” login.
  4. Back up the database, then drop it.
  5. Drop the login.
  6. Restore the database.

I will say that steps 4 and 6 aren’t strictly necessary; just dropping the login will orphan the user. But I’d like to drill the idea of orphans being associated with restores, because that’s the most common scenario in real life.

Important: ALWAYS review code before you run it, even on a test instance. 

Now let’s resolve a single orphaned user

When you have an orphaned user, it’s really easy to detect and fix them. In our case, we’d find the orphan by running

EXEC OrphanedUserDemo..sp_change_users_login 'Report';

And then, we could fix that orphan by first creating the missing login, and then running

EXEC OrphanedUserDemo..sp_change_users_login 'AUTO_FIX', 'OliverTwist';

(Or, if we want the missing login to be created automatically, then “EXEC OrphanedUserDemo..sp_change_users_login ‘AUTO_FIX’, ‘OliverTwist’, NULL, ‘NewPasswordOMG!!!';“)

But this is a manual process, and therefore slow and tedious and not entirely worth our time.

Let’s resolve many orphaned users

Create the stored procedure sp_FixOrphanedUsers in master, and run it as [DBName]..sp_FixOrphanedUsers, and it fixes all orphaned users in that database, if it can do so automatically.

Better still, you could run sp_FixOrphanedUsersAllDB (included) to run this process against all databases on the SQL Server instance.

If you have a regular refresh process – like restoring a set of databases to UAT – you could create a second step in the job to run sp_FixOrphanedUsersAllDB, and greatly simplify your life.

Limitations and caveats

Of COURSE there are limitations, silly reader!

  • Don’t trust code you download from the web. ALWAYS review code before you run it, even on a test instance.
  • This is the first iteration of the procedure(s). Doubtless, you and other readers will have helpful suggestions on how to improve the thing.
  • In this iteration, the SP doesn’t have the ability to specify a password to auto-create missing logins. I think this is a really bad practice. (“Oh, this server doesn’t have a login for ‘GodlyAdminGuy’? Let’s create on with ‘P@ssw0rd!’ for the default!” Yeah, no.)
  • And other things I haven’t yet thought of, but will doubtless be pointed out to me enthusiastically and repeatedly. Feel free, but be cool.

Downloads

Happy days,
Jen McCown
http://www.MidnightDBA.com/Jen

*PITA = “Pain In The Analytics”, so far as you know.

** GET IT??

Applied SQL: LIKE ‘whatever’

SSMS_practiceToday let’s play around with the LIKE operator. Like, totally.

Like, Introduction

Like “determines whether a specific character string matches a specified pattern. A pattern can include regular characters and wildcard characters.” That makes it pretty darn useful, say, when we’re searching for all product reviews with the word “worst” in it:

SELECT ID, Comments
FROM Review
WHERE Comments LIKE ‘%worst%';

Also, when we’re searching for all product names that begin with the word “Hex”:

SELECT ID, [Name]
FROM Product
WHERE [Name] LIKE ‘Hex%';

We can even use multiple % wildcards to find strings where something is followed by something else. This is particularly useful, I find, when searching sys.sql_modules for code within stored procedures:

SELECT object_id, definition
FROM sys.sql_modules
WHERE definition like ‘%DELETE%Customer%';

You get the idea. You can also, of course, find strings that don’t match a certain pattern, using NOT LIKE. For example, let’s say we want all departments that aren’t production related:

SELECT [Name]
FROM Department
WHERE [Name] NOT LIKE ‘%Production%';

Like, Really Cool

But wait, there’s more!

Go back and look over that TechNet article on LIKE. Check out the table in the “pattern” section. We’re familiar with the % wildcard – “Any string of zero or more characters”. But pay attention to the next one: the underscore (_), which represents a single character.

Now we can do things like, oh, getting all strings that begin with “t” and are exactly five characters long:

SELECT petName
FROM myPet
WHERE petName LIKE ‘t____';

You can, of course, use WHERE LEN(petName) = 5 AND petName LIKE ‘t%’ instead. Nothing’s stopping you. But never overlook the beauty of being able to do things in more than one way.

Edit: Someone over on Reddit pointed out that this comment deserves a little more explanation. He’s right: you should note that LEN(petName)=5  makes the predicate non-sargable, meaning that that bit won’t be able to take advantage of a useful index. However, petName LIKE ‘_____’ is ALSO non-sargable, though it does seem to provide a better estimated number of rows, which would potentially result in a better plan.

In our scenario, this is all slightly moot, because that leading t IS a sargable search term: it will use an appropriate index, if available, to seek out data. Even so, I’d probably go with LIKE ‘t____’, knowing what I know now about the estimated rows accuracy.

We also have the ability to search for character ranges:

SELECT petName
FROM myPet
WHERE petName LIKE ‘[D-R]ex';

This will return any instances of Dex, Hex, Lex, Mex, Rex, and so on…but not Bex or Wex.

Go thou, and and play around with, like, whatever.

Happy days,
Jen McCown
MidnightDBA.com/Jen

 

Applied SQL: Find and replace using regular expressions in SSMS

ssms_regexRegular expressions are searches on steroids, the wildcats of the wildcard world*.  Even if you  never ever write CLR, regex (as it’s affectionately known) can be useful to you today, right now.

  1. Open a new query window in SQL Server Management Studio.
  2. Type “xyz”, hit enter twice, and type “xyz” again.
  3. Now hit CTRL-H to pull up your Find and Replace dialogue.
  4. Under Find What, type \n\n. Under Replace With, type \n
  5. Select Options > Use > Regular Expressions.
  6. Hit Replace All. Watch your double spaced script magically turn single spaced.

This is the first of many simple uses for regex in SSMS. With just a little poking around online, you can find every reference to a table in a script, regardless of whether it’s bracketed or not ([stats].Tbl and stats.Tbl and stats.[Tbl], etc.).  Or, replace all instances of varchar(…) with varchar(500) in your stored procedure. Or, well, whatever you need!

Go on, play around with some regex. Check out Technet’s “Search Text with Regular Expressions” and Simple Talk’s “RegEx-Based Finding and Replacing of Text in SSMS” for more.

And…

Happy days,
Jen McCown
http://www.MidnightDBA.com/Jen

P.S. As long as we’re on useful work habits, you should really Learn to Type and get to know common (and custom) keyboard shortcuts, too.

*Oh, what alliteration!!

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November 3-7: PASS Summit, Seattle, WA

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Cunningham’s Law

"The best way to get the right answer on the Internet is not to ask a question, it's to post the wrong answer."
Relevant: http://xkcd.com/386/