Default Schemas In SQL Server

Daniel Hutmacher looks at specifying default schemas on a database:

If your user is a database owner, (i.e. is a member of the db_owner group or has CONTROL permissions on the database) the default schema will always be dbo. This is something you can’t change.

So if your legacy application needs quasi-administrative privileges in the database, you can’t make it a database owner, but you can grant those permissions on the schema instead (which is actually a better idea anyway).

What Daniel is doing is akin to the pre-2005 concept of user spaces, where Bob had a schema and Mary had a schema and Jill had a schema and so forth.

System Objects And Helper Functions

Kenneth Fisher compares and contrasts querying system tables versus using built-in helper functions which query the system tables:

So which should you use? Well, like most things in the database world, it depends. Do you need to cross databases? Do you need to use NOLOCK for a diagnostic query? Do you need additional information available in one of the views that isn’t available in one of the helper functions?

Click through for the comparison.  I agree with his end result, that you should at least know both methods, even if you lean toward one.

COALESCE, ISNULL, And Data Types

Shane O’Neill shows a subtle difference between ISNULL and COALESCE:

You may be asking yourself “What the…?!”.

I asked myself the same question but then I thought of a better idea and asked my Senior the question instead (he usually has better answers than I do), who proceeded to tell me that the final test would only work exactly at midnight!

….so I repeated my question to him.

It’s an interesting read, and not something you’d commonly think about.

Sparklines In R

Robert Sheldon shows how to use SQL Server R Services to display sparklines for categories:

In this article, we continue our discussion on visualizations, but switch the focus to sparklines and other spark graphs. As with many aspects of the R language, there are multiple options for generating spark graphs. For this article, we’ll focus on using the sparkTable package, which allows us to create spark graphs and build tables that incorporate those graphs directly, a common use case when working with spark images.

In the examples to follow, we’ll import the sparkTable package and generate several graphs, based on data retrieved from the AdventureWorks2014 sample database. We’ll also build a table that incorporates the SQL Server data along with the spark graphs. Note, however, that this article focuses specifically on working with the sparkTable package. If you are not familiar with how to build R scripts that incorporate SQL Server data, refer to the previous articles in this series. You should understand how to use the sp_execute_external_script stored procedure to retrieve SQL Server data and run R scripts before diving into this article.

Sparklines and associated visuals have their place in the world.  Read on to see how you can build a report displaying them.

Finding Progress On A Long-Running Statement

David Fowler shows us how to track how far we’ve gotten on a long-running data modification statement:

Well, it would turn out that there is and to find out we need to turn to our trusty friend, the transaction log.

As we know, the transaction log will squirrel away an entry each time that a row is modified.  We can count up all the LOP_MODIFY_ROW, LOP_INSERT_ROW and LOP_DELETE_ROWS entries for our transaction and that will tell us just how many rows our transaction has altered so far.

Click through for a script, as well as an important disclaimer.

Finding Broken Views

Bill Fellows has a script to test each view to see if it is broken:

Shh, shhhhhh, we’re being very very quiet, we’re hunting broken views. Recently, we were asked to migrate some code changes and after doing so, the requesting team told us we had broken all of their views, but they couldn’t tell us what was broken, just that everything was. After a quick rollback to snapshot, thank you Red Gate SQL Compare, I thought it’d be enlightening to see whether anything was broken before our code had been deployed.

You’ll never guess what we discovered.

Read on to see what they discovered (spoilers:  broken views) and how Bill fixed the problem.

Why Window Functions Can’t Appear In The WHERE Clause

Doug Lane explains why window functions like ROW_NUMBER() cannot appear in the WHERE clause (or FROM, GROUP BY, or HAVING):

SQL Server doesn’t process parts of a query in the same order they’re written. Rather than start with SELECT the way we read and write it, here’s the order SQL Server progresses through:

  1. FROM
  2. WHERE
  3. GROUP BY
  4. HAVING
  5. SELECT
  6. ORDER BY
  7. TOP

The first four steps are all about getting the source data and reducing the result set down. Steps 5 & 6 determine which columns are presented and in which order. Step 7 (TOP) is only applied at the end because you can’t say which rows are in the top n rows until the set has been sorted. (You can read Itzik Ben-Gan’s explanation of this process in way more detail here.)

Definitely worth reading.  Doug also shows how to get around this fact of life and get the equivalent of a window function inside a WHERE clause, at least in terms of function if not necessarily performance.

Concatenation Truncation

Adrian Buckman walks through one of the more annoying aspects of building large strings in SQL Server:

So there I was building this massive VARCHAR(MAX) string and concatenated at various points in my code were Database names of the datatype NVARCHAR(128).
The interesting part was that I was expecting SQL server to use my largest data type – the VARCHAR(MAX) and just concatenate the NVARCHAR(128) values into it
this was not the case – what actually happened was my string of  VARCHAR(MAX) characters being truncated down to an NVARCHAR(4000)!

There is a reason for this and its all to do with Data Type Precedence in this case the NVARCHAR is preceding my VARCHAR unless of course I explicitly convert the NVARCHAR to a VARCHAR.

Read the whole thing.

Listing SQL Server Options

Kenneth Fisher breaks apart the @@OPTIONS bit flags:

There are a fair number of options settings. ANSI_NULLS, ARITHABORT, QUOTED_IDENTIFIER, etc. Each session has its own set of configurations. They are initially set based on the user settings system configuration, then the various connection programs (SSMS for example) can override that, then the various SETcommands can override that.

Now personally I prefer to keep my settings to the default to eliminate confusion but they do get changed occasionally. Just as a for example, when you generate a script from SSMS it typically includes a bunch of SET ON and SET OFF commands. And if you turn on a setting that was already on, then turn it off and the end, well, your setting has changed unexpectedly. My original intent for this post was to create a stored procedure that would let you save the current settings and restore them. Unfortunately, I ran into a scope problem. I can find the current settings: @@options. I can break down the integer value using a script from here (just in case the post should disappear before this one does here is the code from the article)

Read on for the list, including things like ANSI_NULLS, ANSI_PADDING, and XACT_ABORT.  I probably pay less attention to these than I should and just have a habit of setting the few most important settings for my environment atop every procedure definition.

Using RAISERROR For Debug Info

Doug Lane exhorts people to use RAISERROR instead of PRINT when printing messages:

It wasn’t until a few years ago, when I started contributing to the First Responder Kit at Brent Ozar Unlimited, that I noticed every status message in the kit scripts was thrown with something other than PRINT.

Strange, I thought, since those scripts like to report on what statements are running. Turns out, they avoided PRINT because it has some serious drawbacks:

  • PRINT doesn’t necessarily output anything at the moment it’s called.
  • PRINT statements won’t show up in Profiler.
  • PRINT can’t be given variable information without CAST or CONVERT.

Those are important limitations, as Doug shows.

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