Querying SQL Server with Golang

Words: 333

Time to read: ~ 2 minutes

I’ve been looking into Golang recently. Hey, everyone has to go with what interests them!

It’s all very well and good to open up Golang and write a FizzBuzz (note to self: write a FizzBuzz), but I still work with databases.

So before I do anything with Golang, I’d like to know: can it interact with databases.

Granted, everything can, but how easy is it? And does trying to interact with databases kill any interest I have in the language.

So, let’s give it a go.

First, some caveats.

You have to install Go (shocking, I’m aware).
This post is effectively me reading the tutorials on the Golang website and converting it to work with SQL Server.
You have to do some funky stuff to get the driver for SQL Server; granted, funky things basically mean run go get <Github link>. I’ve done funkier…
There’s also some better way to do this, but who cares. This is exploratory.
When setting up my SQL instances, I did some weird thing where I now have to specify a non-standard port when connecting. So I have to open up the error log in SQL Server, see what port it’s listening to, and put that into the code. Yes, I’m aware that I’m a DBA, and I should be able to fix this, but it’s my personal time & my personal test instance. I’ll fix it when I want to.

Anyway, here’s the code.

Do with it what you will; I’m just happy it works, and I’m delighted that I’m excited about it!

	package main

	import (
	"database/sql"
	"fmt"
	"log"

	// this is the driver & yes, even though we're throwing
	// it away to `_`, it's still needed
	_ "github.com/denisenkom/go-mssqldb"
	)

	var (
	db *sql.DB
	server = "localhost"
	// Yes, I hate this too…
	port = 60515
	)

	func main() {
	// Build connection string
	connString := fmt.Sprintf(
	"server=%s;port=%d;Trusted_Connection=True;AppName='Golang'",
	server,
	port,
	)

	// I want the line that the error occurs in my logs, please & thank you
	log.SetFlags(log.Lshortfile)

	// Create connection pool
	var err error
	db, err = sql.Open("sqlserver", connString)
	if err != nil {
	log.Fatalln("Creating connection pool failed:", err.Error())
	}

	stringDate, err := getDate()
	if err != nil {
	log.Fatalln("getDate() failed:", err.Error())
	}

	fmt.Println("Read:", stringDate)
	fmt.Println("Read rows successfully!")
	fmt.Println("Finished.")
	}

	func getDate() (string, error) {
	var dte string

	// We're "scanning" the values from the query into the `dte`
	// variable using `&<var name>`. Different, but interesting…
	if err := db.QueryRow("SELECT dt = SYSDATETIME();").Scan(&dte); err != nil {
	return "false", fmt.Errorf("getDate() function failed! %s", err.Error())
	}

	return dte, nil
	}

view raw db.go hosted with ❤ by GitHub

First of all, what happens when it works?

go run main.go

And what happens when it fails, say cause the default port actively refuses connections?!

// changing `port = 60515` -> `port = 60514`

Happy out! Now to see what else we can do. Thankfully, I’ve somehow managed to get some ideas marinating in creative juices. Let’s see if I have the time and the energy to see them through!

T-SQL Tuesday #152

Words: 375

Time to read: ~ 3 minutes

I don’t know if this post is a rage against “database-ubiquitous” SQL or Object-Relational Mapping tools (ORMs)

I’m going to say that it’s a rant against the first because if you know what you are doing, then ORMs won’t be a performance concern

But people use ORMs instead of Stored Procedures because
Them: “what happens if we need to change databases? We don’t have to worry about that now cause they’ll be baked in the application, and we won’t have to recreate the Stored Procedures in the new database cause ORMs just work!”

Everything just works until it doesn’t

I’ve worked with several companies and heard this argument many times from developers

Part of why I’m ranting about database-ubiquitousness SQL instead of ORMs is that I’ve also witnessed SQL code that has to work everywhere

I’m going to call this SQL “DUh SQL” from now on since I only have so many vowels on my keyboard and shouldn’t waste them re-writing the word “ubiquitousness”

Them: “Nope, we can’t use DATEFROMPARTS; it’s not available in other databases! Yeah, we use GETDATE() everywhere; what’s your point? WHAT!?!”

I’ve moved across different cloud providers more than I’ve moved databases, and guess what? Each cloud provider move, we’ve kept the same database

I know that knowledge sharing “in the wild” says that you should use ORMs or DUh SQL
The route to a 10x engineer is paved in DRY, KISS, and SWALK
Well, maybe not SWALK

Them: “But the leading minds out there say that you should keep it DUh since that means it’ll be a breeze if we have to move databases”

Sure, and I’ve been told that ice baths help in recovery
I’m not going to take them, though, since I know there’s a difference between me trying to do a 5k and dedicated athletes!

I love arguing with people in my blog posts; I rarely lose

So, don’t use DUh SQL cause of reasons that may not apply to you
Don’t refuse performance tuning efforts if they’ll add database-specific code
And, please, learn to use your tools

Oh, and apologies for the lack of full-stops, I can’t use them in case I have to turn this post into regex

Table Column Differences Part 03 – Compare-SqlTableColumns

Words: 470

Time to read: ~ 2 minutes

Don’t talk to me about it!

Four years ago (I know, where did the time go?), I wrote about Table Column Differences with T-SQL and PowerShell.

A Michal commented on the post, asking how to get a specific output from his search.

Hi,
Thanks for your sharing. What if I also want to compare case sensitively columns and the order of them (syncwindows). How can I presented it on powershell.
I mean that in the final table I want to show also something like: column_a, column_A –> case sensitive
AND
column_a, column_a –> different order in the table
Thanks in advance
Michal

I confess that I never got around to answering Michal until a few weeks ago when I found myself with some rare free time.

Since then, I’ve written a script, slapped it into a function, and threw it up on Github.

Here’s hoping that it does what you want this time Michal, thanks for waiting.

Shall I Compare Thee to Another Table?

The first thing that we need to do is have a couple of SQL tables to compare.

So, I threw up a Docker container and created a couple of tables with nearly the same layout.

(Get-DbaDbTable -SqlInstance localhost -Table 'dbo.DifferenceTable01', 'dbo.DifferenceTable02').Columns |
        Select-Object -Property Parent, Name, ID, DataType |
        Format-Table -GroupBy Parent

I’m liking the new PowerShell formatting

You can see that there are around three differences here

Column orders, e.g. col9 has id 6 in dbo.DifferenceTable01 but id 5 in dbo.DifferenceTable02.
Column case sensitivity, e.g. col7 does not match COL7.
Column presence, e.g. col3 doesn’t exist in dbo.DifferenceTable01 at all.

While Compare-Object has the -CaseSensitive switch, I don’t think that it would be helpful in all these cases. Or else I didn’t want to use that command this time around.

So, I wrote a function to get the output we wanted, and yes, I now include myself among that list of people wishing for that output.

I’m allowed to be biased towards the things that I write 🙂

Compare-SqlTableColumns

Compare-SqlTableColumns -SqlInstance localhost -Table1 'dbo.DifferenceTable01' -Table2 'dbo.DifferenceTable02' |
        Format-Table

I’ve tried to include everything you could want in the function output, i.e. column names, column ids, and statuses.

Something I’ve started to do lately is wrapping a [Diagnostics.StopWatch] in my verbose statement to see where potential slow parts of the function are.

I’d like to think that 0.2 seconds for this example aren’t too bad.

$x = Compare-SqlTableColumns -SqlInstance localhost -Table1 'dbo.DifferenceTable01' -Table2 'dbo.DifferenceTable02' -Verbose

$x | Format-Table

Thou hast less columns than thine brother…

Feel free to use and abuse this function to your hearts content. I know that there are a few things that I’d add to it. Comparing across different instances being an obvious one that I’d like to put in.

Hopefully though, someone out there will find it helpful.

Here’s looking at you, Michal.

Finding Parameters that do not match Column Names

You think this will take me hours? Ha! Think again.

Words: 437

Time to read: ~ 2 minutes

Script Link: https://github.com/shaneis/RandomScripts/blob/master/WhereParameterNameDoesNotMatchColumnName.ps1

Continue reading “Finding Parameters that do not match Column Names”

ARIGHTABORT-ing & Anti-ANSI_WARNINGS

I recently ran into a problem with the QUOTED_IDENTIFIERS option in SQL Server, and it got me to thinking about these SET options.

I mean the fact that, on tables where there are filtered indexes or computed columns with indexes, QUOTED_IDENTIFIER is required to be on to create any other indexes is just not intuitive. But if you can’t create indexes because of it then I’d argue that it’s pretty damn important! I also found out that this problem is not just limited to QUOTED_IDENTIFIER but to ARITHABORT and ANSI_WARNINGS as well.

Just check out the Microsoft Docs and what it has to say about it:

SET ARITHABORT must be ON when you are creating or changing indexes on computed columns or indexed views. If SET ARITHABORT is OFF, CREATE, UPDATE, INSERT, and DELETE statements on tables with indexes on computed columns or indexed views will fail.

And for ANSI_WARNINGS it says:

SET ANSI_WARNINGS must be ON when you are creating or manipulating indexes on computed columns or indexed views. If SET ANSI_WARNINGS is OFF, CREATE, UPDATE, INSERT, and DELETE statements on tables with indexes on computed columns or indexed views will fail.

It’s not just Indexes

So, like a dog when it sees a squirrel, when I found out about the problems with ARITHABORT and ANSI_WARNINGS I got distracted and started checking out what else I could break with it. Reading through the docs, because I found that it does help even if I have to force myself to do it sometimes, I found a little gem that I wanted to try and replicate. So here’s a reason why you should care about setting ARITHABORT and ANSI_WARNINGS on.

Default to on

At one stage or another if you’re working with SQL Server, you’ve probably encountered the dreaded “Divide By 0” error:

Msg 8134, Level 16, State 1, Line 4
Divide by zero error encountered.

If you want to check this out, then here’s the code below for our table:


USE Pantheon;

-- Create our test table...
CREATE TABLE dbo.ArithAborting (
    id tinyint NULL
);
GO

And our attempt at inserting that value into the table:

SET ARITHABORT ON;
GO
SET ANSI_WARNINGS ON;
GO
-- Check can we insert a &quot;divide by 0&quot;...
BEGIN TRY
INSERT INTO dbo.ArithAborting (id) SELECT 1/0;
END TRY
BEGIN CATCH
  PRINT 'NOPE!';
  THROW;
END CATCH;

And we get our good, old, dreaded friend:

We check our ArithAborting table and nothing is there, like we expected!

SELECT *
FROM dbo.ArithAborting;

What about if we were to turn our ARITHABORT and ANSI_WARNINGS off though, what happens then? Well that’s a simple thing to test, we just turn them off and run the script again:

--Turn ARITHABORT off;
SET ARITHABORT OFF;
GO
SET ANSI_WARNINGS OFF;
GO
-- ...insert into our table...
BEGIN TRY
  INSERT INTO dbo.ArithAborting (id) SELECT 1/0;
END TRY
BEGIN CATCH
  PRINT 'NOPE!';
  THROW;
END CATCH;

Now before I freak out and start thinking that I’ve finally divided by zero, let’s check the table:

What’s going on here? Checking the docs…

During expression evaluation when SET ARITHABORT is OFF, if an INSERT, DELETE or UPDATE statement encounters an arithmetic error, overflow, divide-by-zero, or a domain error, SQL Server inserts or updates a NULL value. If the target column is not nullable, the insert or update action fails and the user receives an error.

Do I like this?

Nope!

If I have a terminating error in my script, I quite like the fact that SQL Server is looking out for me and won’t let me put in bad data, but if you have these options turned off, even if you wrap your code in an TRY...CATCH block, it’s going to bypass it.

Plus if you are trying to divide by 0, please stop trying to break the universe. Thank you.

Comparing Column Values in the Same Table

The Set-Up:

This is yet another time that a blog post has come about from a question by a developer. They’re good guys, I guess, they keep me on my toes.

This time it was with change logging. We didn’t have Change Data Capture (CDC), or Temporal Tables enabled (have you seen the YouTube videos by Bert Wagner ( blog | twitter ) on these?). What we did have was “manual logging” and no, I’m not even talking about Triggers.

What we had was INSERT statements, directly after a MERGE statement, that inserted into a table variable a hard-coded name of the column, the old value, and the new value.

Is that what I would do? Doesn’t matter, it was there before I got there, seems to work, and is low down on the list of priorities to change.

The question was, every time that they needed to add a column to a table, and change log it, they had to add multiple lines to the change tracking procedure and the procedure was getting gross and hard to maintain.

Something to do with DRYness?

Create Table:

You know the drill by now, I quite like to play along so let us facilitate that (from now on I’m going to use Gist, formatting with native WordPress is starting to annoy me).

	USE Pantheon;
	GO

	DROP TABLE IF EXISTS dbo.GotAnyChange;

	CREATE TABLE dbo.GotAnyChange
	(
	GotAnyChangeID int IDENTITY(1, 1),
	Column1 int,
	Column2 char(1),
	Column3 date,
	Column4 bigint,
	Column5 varchar(50),
	Column6 datetime
	);

	INSERT INTO dbo.GotAnyChange
	( Column1,
	Column2,
	Column3,
	Column4,
	Column5,
	Column6
	)
	VALUES
	(0, — Column1 – int
	'A', — Column2 – char(1)
	GETDATE(), — Column3 – date
	0, — Column4 – bigint
	REPLICATE('A', 50), — Column5 – varchar(50)
	GETDATE() — Column6 – datetime
	);

	SELECT *
	FROM dbo.GotAnyChange;

view raw

CreateGotAnyChange.sql

hosted with ❤ by GitHub

This will create our table and, luckily, all of it’s columns are important enough to warrant capturing when they get changed.

FirstCreation — Despite their looks, these values are “important”

Old, Way WHERE old=way

Let’s take a look at the code that they were using, shall we?

	USE Pantheon;
	GO

	DECLARE @Id int = 1

	— ChangeLog data store
	— Yes, I know that they're all varchars…
	DECLARE @ChangeLogTemp table
	(
	ColumnName varchar(100),
	OldValue varchar(20),
	NewValue varchar(20)
	);

	— Old & New value data store
	DECLARE @OutputTemp table
	(
	OldColumn1 int NOT NULL,
	NewColumn1 int NOT NULL,
	OldColumn2 char(1) NOT NULL,
	NewColumn2 char(1) NOT NULL,
	OldColumn3 date NOT NULL,
	NewColumn3 date NOT NULL,
	OldColumn4 bigint NULL,
	NewColumn4 bigint NULL,
	OldColumn5 varchar(50) NOT NULL,
	NewColumn5 varchar(50) NOT NULL,
	OldColumn6 datetime NULL,
	NewColumn6 datetime NULL
	);

	— Actual update, outputting the old and new values
	UPDATE gac
	SET gac.Column1 = 1,
	gac.Column2 = 'B',
	gac.Column6 = GETDATE()
	OUTPUT Deleted.Column1, Inserted.Column1,
	Deleted.Column2, Inserted.Column2,
	Deleted.Column3, Inserted.Column3,
	Deleted.Column4, Inserted.Column4,
	Deleted.Column5, Inserted.Column5,
	Deleted.Column6, Inserted.Column6
	INTO @OutputTemp
	FROM dbo.GotAnyChange AS gac
	WHERE gac.GotAnyChangeID = @Id;

	— Capture changes. 1 for each column we want to capture
	INSERT INTO @ChangeLogTemp
	SELECT 'Column1',
	OldColumn1,
	NewColumn1
	FROM @OutputTemp
	WHERE ISNULL(OldColumn1, NewColumn1) <> NewColumn1;

	INSERT INTO @ChangeLogTemp
	SELECT 'Column2',
	OldColumn2,
	NewColumn2
	FROM @OutputTemp
	WHERE ISNULL(OldColumn2, NewColumn2) <> NewColumn2;

	INSERT INTO @ChangeLogTemp
	SELECT 'Column3',
	OldColumn3,
	NewColumn3
	FROM @OutputTemp
	WHERE ISNULL(OldColumn3, NewColumn3) <> NewColumn3;

	INSERT INTO @ChangeLogTemp
	SELECT 'Column4',
	OldColumn4,
	NewColumn4
	FROM @OutputTemp
	WHERE ISNULL(OldColumn4, NewColumn4) <> NewColumn4;

	INSERT INTO @ChangeLogTemp
	SELECT 'Column5',
	OldColumn5,
	NewColumn5
	FROM @OutputTemp
	WHERE ISNULL(OldColumn5, NewColumn5) <> NewColumn5;

	INSERT INTO @ChangeLogTemp
	SELECT 'Column6',
	OldColumn6,
	NewColumn6
	FROM @OutputTemp
	WHERE ISNULL(OldColumn6, NewColumn6) <> NewColumn6;

	— Capture all changes as an XML
	SELECT ColumnName AS CN,
	OldValue AS OV,
	NewValue AS NV
	FROM @ChangeLogTemp
	FOR XML PATH('Change'), ROOT('Changes');

view raw

OldWayChangeCapture.sql

hosted with ❤ by GitHub

And the results?

You can probably see the problem here.

Hey! It’s legacy code, let’s focus on just 1 problem at at time!

The main issue that I was asked about was every time a column was deemed important and needed to be added to the list, they had to insert another INSERT INTO @ChangeLogTemp... and they thought that it wasn’t sustainable in the long run.

Hmmm it also comes across as very RBAR doesn’t it? Every time we want to include another column to the change tracking, we have to add them row by agonizing row. The script is already big enough, if we keep adding more, it will get massive!

Set based is 90% of the time the right way to go but how do we do set based solutions on the same table?

New JOIN Way ON new = way

The first thing I do is to change that table variable into a temp table. Stats, indexes (if necessary), and I can query the results as we go along. Much better!

The second thing is that, whether by luck or by design, the legacy code has the same naming conventions for the columns; new column values are have the prefix “New%” in the column name and old columns have the “Old%” prefix.
This works for us because we can now split the new columns into 2 derived tables, New and Old, and that way we have the differences.

PreUnPivotColumns — Potential problem here…

Have you ever tried to find the differences between two consecutive rows of data? It’s fiendishly difficult. WHERE Column1 on row1 != Column1 on row2 apparently just does not work, le sigh.

I’ve talked before about PIVOT but now I’m going to introduce you to it’s little brother, UNPIVOT, which “rotating columns of a table-valued expression into column values”

I say “little brother” because the whole document talks about PIVOT, with only brief mentions of UNPIVOT in the notes.

If you’re writing documentation like this, please stop.

With UNPIVOT we can create a table of our rows around our ID and Column names…

UnpivotedColumns — Potential problem averted!

… and with this, we can join on our ID and Column names and get to our more intuitive WHERE OldValue != NewValue.

Bringing it all together!

	USE Pantheon;
	GO

	DECLARE @ChangeLogAsXml xml,
	@Id int = 1;

	DROP TABLE IF EXISTS #OutputTableNew;
	CREATE TABLE #OutputTableNew
	(
	GotAnyChangeID int NOT NULL,
	OldColumn1 int NOT NULL,
	NewColumn1 int NOT NULL,
	OldColumn2 char(1) NOT NULL,
	NewColumn2 char(1) NOT NULL,
	OldColumn3 date NOT NULL,
	NewColumn3 date NOT NULL,
	OldColumn4 bigint NULL,
	NewColumn4 bigint NULL,
	OldColumn5 varchar(50) NOT NULL,
	NewColumn5 varchar(50) NOT NULL,
	OldColumn6 datetime NULL,
	NewColumn6 datetime NULL
	);

	UPDATE gac
	SET gac.Column1 = 2,
	gac.Column2 = 'C',
	gac.Column6 = GETDATE()
	OUTPUT inserted.GotAnyChangeID,
	Deleted.Column1, Inserted.Column1,
	Deleted.Column2, Inserted.Column2,
	Deleted.Column3, Inserted.Column3,
	Deleted.Column4, Inserted.Column4,
	Deleted.Column5, Inserted.Column5,
	Deleted.Column6, Inserted.Column6
	INTO #OutputTableNew
	FROM dbo.GotAnyChange AS gac
	WHERE gac.GotAnyChangeID = @Id;

	SELECT New.ColumnName AS CN,
	New.NewValue AS NV,
	Old.OldValue AS OV
	FROM
	(
	SELECT Unpvt.GotAnyChangeID,
	Unpvt.ColumnName,
	Unpvt.NewValue
	FROM
	( SELECT [GotAnyChangeID],
	CAST(ISNULL([NewColumn1], '') AS nvarchar(20)) AS [Column1],
	CAST(ISNULL([NewColumn2], '') AS nvarchar(20)) AS [Column2],
	CAST(ISNULL([NewColumn3], '') AS nvarchar(20)) AS [Column3],
	CAST(ISNULL([NewColumn4], '') AS nvarchar(20)) AS [Column4],
	CAST(ISNULL([NewColumn5], '') AS nvarchar(20)) AS [Column5],
	CAST(ISNULL([NewColumn6], '') AS nvarchar(20)) AS [Column6]
	FROM #OutputTableNew
	) AS DataSource UNPIVOT(NewValue FOR ColumnName IN([Column1], [Column2], [Column3], [Column4], [Column5], [Column6])) AS Unpvt
	) AS New
	INNER JOIN
	(
	SELECT Unpvt.GotAnyChangeID,
	Unpvt.ColumnName,
	Unpvt.OldValue
	FROM
	( SELECT [GotAnyChangeID],
	CAST(ISNULL([OldColumn1], '') AS nvarchar(20)) AS [Column1],
	CAST(ISNULL([OldColumn2], '') AS nvarchar(20)) AS [Column2],
	CAST(ISNULL([OldColumn3], '') AS nvarchar(20)) AS [Column3],
	CAST(ISNULL([OldColumn4], '') AS nvarchar(20)) AS [Column4],
	CAST(ISNULL([OldColumn5], '') AS nvarchar(20)) AS [Column5],
	CAST(ISNULL([OldColumn6], '') AS nvarchar(20)) AS [Column6]
	FROM #OutputTableNew
	) AS DataSource UNPIVOT(OldValue FOR ColumnName IN([Column1], [Column2], [Column3], [Column4], [Column5], [Column6])) AS Unpvt
	) AS Old
	ON Old.ColumnName = New.ColumnName
	AND Old.GotAnyChangeID = New.GotAnyChangeID
	WHERE New.NewValue <> Old.OldValue
	FOR XML PATH('Change'), ROOT('Changes');

view raw

NewWayChangeCapture.sql

hosted with ❤ by GitHub

And it works!

NewWayResult — wasn’t this replaced by JSON?

It’s not great though.

The whole thing was supposed to be to reduce the amount of changes required when they need to include or exclude columns. All in all though, it’s just 6 lines less. Not exactly the great return that you’d expect.
Yeah, true with the old way for every column we want to add we have to add an extra 6 lines while the new way adds 2.

That means for 1,024 columns:

The old way could have at least 6,144 lines per table. (1024 * 6)
The new way could have at least 2,048 lines per table (not explaining this calculation >:( )

So, is there anything else that we can do?

Dynamically?

I’ve talked before about T-SQL automation with Dynamic SQL and this should be a good candidate for that.

What can we make dynamic here though? How about…

The new and old columns bit?
The FOR ColumnName IN([Column1], [Column2], [Column3], [Column4], [Column5], [Column6]) bit?
The CAST(ISNULL([Old/NewColumn], '') AS nvarchar bit?

Explain it to me.

The new and old columns.

Well, temp tables exist in the tempdb database, they just get a suffix of a lot of underscores and a hex value.

So to get our column names, we can just query the sys.tables and sys.columns catalog views in [tempdb] and we should have what we need.

DynamicColumnsResults — We can add a filter clause too

2. The FOR ColumnName IN (

I’ve talked before about concatenating values so we can use that to generate this part of the script.

DynamicUnpivotColumnNames — LEN(tc.name) – 3 to remove the “old”/”new” prefix

3. The CAST(ISNULL(...

This is basically the same as the above. Don’t be put off by needing to add CAST(ISNULL( before the column names, it’s not as complex as you’d think.

DynamicNewColumnsSelect — STUFF just doesn’t look as pretty… 🙁

Now that we have our dynamic bits, let’s create the full statements.

Full Dynamic Script

	USE Pantheon;
	GO

	DROP TABLE IF EXISTS #OutputTableDynamic;
	GO
	CREATE TABLE #OutputTableDynamic
	(
	GotAnyChangeID int NOT NULL,
	OldColumn1 int NOT NULL,
	NewColumn1 int NOT NULL,
	OldColumn2 char(1) NOT NULL,
	NewColumn2 char(1) NOT NULL,
	OldColumn3 date NOT NULL,
	NewColumn3 date NOT NULL,
	OldColumn4 bigint NULL,
	NewColumn4 bigint NULL,
	OldColumn5 varchar(50) NOT NULL,
	NewColumn5 varchar(50) NOT NULL,
	OldColumn6 datetime NULL,
	NewColumn6 datetime NULL
	);

	DECLARE @ChangeLogAsXml xml,
	@Id int = 1;

	UPDATE gac
	SET gac.Column1 = 3,
	gac.Column2 = 'D',
	gac.Column6 = GETDATE()
	OUTPUT inserted.GotAnyChangeID,
	Deleted.Column1, Inserted.Column1,
	Deleted.Column2, Inserted.Column2,
	Deleted.Column3, Inserted.Column3,
	Deleted.Column4, Inserted.Column4,
	Deleted.Column5, Inserted.Column5,
	Deleted.Column6, Inserted.Column6
	INTO #OutputTableDynamic
	FROM dbo.GotAnyChange AS gac
	WHERE gac.GotAnyChangeID = @Id;

	DECLARE @DynamicSql nvarchar(MAX),
	@NewColumns nvarchar(MAX),
	@OldColumns nvarchar(MAX),
	@columns nvarchar(MAX);

	SET @NewColumns =
	(
	SELECT STUFF(
	(
	SELECT TOP (1024)
	', CAST(ISNULL(' + QUOTENAME(RIGHT(tc.name, LEN(tc.name))) + ', '''') AS nvarchar(20)) AS '
	+ QUOTENAME(RIGHT(tc.name, LEN(tc.name) – 3))
	FROM tempdb.sys.tables AS tt
	INNER JOIN tempdb.sys.columns AS tc
	ON tt.object_id = tc.object_id
	WHERE tt.name LIKE '#OutputTableDynamic%'
	AND tc.name LIKE 'New%'
	ORDER BY tc.column_id
	FOR XML PATH('')
	), 1, 2, ''));
	SET @OldColumns =
	(
	SELECT STUFF(
	(
	SELECT TOP (1024)
	', CAST(ISNULL(' + QUOTENAME(RIGHT(tc.name, LEN(tc.name))) + ', '''') AS nvarchar(20)) AS '
	+ QUOTENAME(RIGHT(tc.name, LEN(tc.name) – 3))
	FROM tempdb.sys.tables AS tt
	INNER JOIN tempdb.sys.columns AS tc
	ON tt.object_id = tc.object_id
	WHERE tt.name LIKE '#OutputTableDynamic%'
	AND tc.name LIKE 'Old%'
	ORDER BY tc.column_id
	FOR XML PATH('')
	), 1, 2, '' ) );
	SET @columns =
	(SELECT STUFF(
	( SELECT TOP (1024)
	', ' + QUOTENAME(RIGHT(tc.name, LEN(tc.name) – 3))
	FROM tempdb.sys.tables AS tt
	INNER JOIN tempdb.sys.columns AS tc
	ON tt.object_id = tc.object_id
	WHERE tt.name LIKE '#OutputTableDynamic%'
	AND tc.name LIKE 'New%'
	ORDER BY tc.column_id
	FOR XML PATH('')
	), 1, 2, ''));
	SET @DynamicSql =
	N'SELECT New.ColumnName AS CN, New.NewValue AS NV, Old.OldValue AS OV FROM (SELECT Unpvt.GotAnyChangeId, Unpvt.ColumnName, Unpvt.NewValue FROM (SELECT [GotAnyChangeId], ' + @NewColumns
	+ N' FROM #OutputTableDynamic ) AS DataSource UNPIVOT (NewValue FOR ColumnName IN (' + @columns
	+ N') ) AS Unpvt ) AS New INNER JOIN ( SELECT Unpvt.GotAnyChangeId, Unpvt.ColumnName, Unpvt.OldValue FROM (SELECT [GotAnyChangeId], ' + @OldColumns
	+ N' FROM #OutputTableDynamic ) AS DataSource UNPIVOT (OldValue FOR ColumnName IN (' + @columns
	+ N')) AS Unpvt) AS Old ON Old.ColumnName = New.ColumnName AND Old.GotAnyChangeId = New.GotAnyChangeId WHERE New.NewValue != Old.OldValue FOR XML PATH(''Change''), ROOT(''Changes'')';

	EXECUTE sp_executesql @DynamicSql;

view raw

DynamicChangeCapture.sql

hosted with ❤ by GitHub

Results are good!

DynamicWayResult — We’ve seen this before

Overall, the script is longer at nearly double the lines but where it shines is when adding new columns.
To include new columns, just add them to the table; to exclude them, just add in a filter clause.

So, potentially, if every column in this table is to be tracked and we add columns all the way up to 1,024 columns, this code will not increase.
Old way: at least 6,144.
New way: at least 2,048.
Dynamic: no change

Summary:

Like the script, this was a massive post. Back at the start, I said that a developer came to me because they wanted to get more DRY (?) and stop needing to add more content to the stored procedure.

Do you think the developer used this?

Nope!

I can’t say that I blame them, it’s slightly ugly and unwieldy, and I wrote it so I should love it.
Yet if something was to go wrong and the need was there to open the procedure and troubleshoot it, the first person to open this up is going to let out a groan of despair!

So this request turned into a proof of concept and nothing more. No skin off my back, I have a growing list of tasks to accomplish by 5 minutes ago. Better get back to them.

Table Column Differences with T-SQL and PowerShell – Part 2

If this was a horror movie, it would be called “The Differencing”…duh duh duh!

Time to read: ~ 5 minutes

Words: 1057

Update 2021-07-14: Marked code blocks as preformatted

The original post for this topic garnered the attention of a commenter who pointed out that the same result could be gathered using a couple of UNION ALLs and those lovely set-based EXCEPT and INTERSECT keywords.

I personally think that both options work and whatever you feel comfortable with, use that.

It did play on my mind though of what the performance differences would be…what would the difference in STATISTICS IO, TIME be? What would the difference in Execution Plans be? Would there even be any difference between the two or are they the same thing? How come it’s always the things I tell myself not to forget that I end up forgetting?

I have no idea about the last one but at least the other things we can check. I did mention to the commentor that I would find this an interesting blog topic if they wanted to give it a go and get back to me. All I can say is – Sorry, your mail must have got lost in transit. I’m sure it is a better blog post that mine anyway.

If you’re going to do it…

For this test, we’re not going to stop at a measely 4 columns per table. Oh no! For this one we’re going to go as wide as we can.

With a recent post by Kenneth Fisher ( blog | twitter ) out about T-SQL FizzBuzz, I’m going to create two tables, both of which will have incrementing column names i.e. col00001, col00002, …, col1024. Table1 will have all columns divisible by 3 removed while Table2 will have all columns divisible by 5 removed.

See, FizzBuzz can be useful!

So our table creation scripts…

SELECT TOP (1024)
    CASE WHEN v.number = 0
        -- Change this to 02 the second run through
        THEN N'CREATE TABLE dbo.TableColumnDifference01 ('
    ELSE N' col' + RIGHT(REPLICATE('0', 8) + CAST(v.number AS nvarchar(5)), 4) + N' int,'
    END
  FROM master.dbo.spt_values AS v
 WHERE v.type = N'P'
   AND (
       -- Change this to '% 5' the second run through
       v.number % 3 != 0
       OR v.number = 0
)
FOR XML PATH('')

NOTE: When you copy and paste the results of this query into a new window to open it, it is going to fail. Why? Well the end of the script is going to be along the lines of colN int, and it needs to be colN int). Why is it like this? Well it was taking to damn long to script that out. Feel free to change this to work for you. Hey if you do, let me know!

Now, how I’m going to do test this, is run each method 3 times (PIVOT, UNION, and PowerShell), then measure the third run of each method. This is mainly as I want to get rid of any “cold cache” issues with SQL Server where the plan has to be compiled or the data brought into memory.

…do it Pivot

So first up is the Pivot method from the last blog post. In case you’re playing along at home (and go on, do! Why should kids get all the fun) here is the code that I’m running.

And here is our results:

PivotMethodGridResults — Yup, those be columns

What we are really after though is the stats, execution plan and time to complete for our 3rd execution. Now as much as I love reading the messages tab for the stats information, I feel with blog posts that aesthetics is king, so I’m going to be using the free tool by Richie Rump ( twitter ) “Statistics Parser“

Stats:

Execution Plan:

PivotMethodGridPlan — Probably the first plan I’ve seen where the SORT isn’t the most expensive!

..do it UNION

Secondly we have what I dubbed “the UNION method” (no points for figuring out why) and the only change I’ve made to this script is to add in PARSENAME() and that’s only so that the script would..you know…work.

Results be like:

UnionMethodGridResults — Yep, Yep, Yep, Yep, Nope, Yep…

Stats:

hmm…less Scan Counts but 5 times the reads…also 5 times slower than the PIVOT method. Maybe the execution plan will be prettier?

Execution Plan:

Yeah…so…that’s…that’s different from the first plan! I was right in my comment though, there is a concatenation operator (there’s actually 2, you may need to zoom in to find them though)

…do it PowerShell

Finally we have the PowerShell method. No messing about here, let’s get straight to it! I’m going to lump all the code together in one gist and I’ll be wrapping it in Measure-Command to get the speed of the command.

Get-Results

PoSHMethodGridResults — Yeah I’m liking VS Code more and more…

Get-Stats:

help execution; help plan

Would you believe that I couldn’t figure out how to get an execution plan for PowerShell 🙂

If anybody knows, hit me up!

Finishing off

You know at the start of this, I was fully expecting the PowerShell to win out, followed by the UNION method, because it’s use of UNION, EXCEPT, and INTERSECT which are basically made for this kind of problem, and the PIVOT method bringing up a distant last since PIVOTs have this complexity stigma attached to them and what is complex is normally slow.

From a sheer speed point of view, the actual results are:

Pivot
PowerShell
Union

Who knew!?

I don’t think this is the end of my use of PowerShell or Union operators though. I’m not going to replace all the stuff that I can with Pivots. For one I just think that PowerShell and the Union operators are just too cool!

I actually like this result for two reasons.

There are multiple way to do something in SQL, there are good ways and better ways. The main point is whatever option you choose, make sure you know what it entails and can justify it.
Whatever works for you, works for you!
You don’t know something, test it and find out! What you think the outcome may be, may not be true.

Now if you’ll excuse me, I want to figure out if there’s a way to return execution plans with PowerShell.

Chaos Theory, Compound Effects, and Consequences.

Straight away I want to apologise for the Nicolas Cage memes!

User Groups are great, aren’t they?

I just got back from the Reading User Group and I’m still in that post “User Group Glow”, also known as “Long Day Lethargy”, or “Twelve Hour Tiredness”.

They are great though! A chance to talk to other people in the SQL Server community, – a slight reminder that even if you work alone, people are still experiencing some of the same problems that you are (apparently everyone has to deal with multiple nested views, who knew!) – a chance to hear presentations on different topics, and pizza if you’re lucky (we were).

I realised during the session that the two presentations given during the User Group had a connection with a small issue with a table change I had been given with a developer.

Here’s what did not happen to me so you can watch out for it.

The Chaos Theory

Raul Gonzalez ( blog | twitter ) was first up with this presentation “Database Design Matters, Seriously”, showing us the chaos that can occur from not giving some serious thought into how you design your database.

His session is not yet up on his blog as I’m writing this but it will be soon so keep an eye out for that!

Now he had a lot of good points but, for brevity’s sake, the main chaos theory points here are what happens if you don’t take advantage of CHECK CONSTRAINTS, FOREIGN KEY CONSTRAINTS, and not specifying a columns NULLABILITY (yes, that’s a word!). SQL Server is a powerful program with many performance optimizations provided for you, but it’s not omniscient; it can only use the information that you give it!

His points on NULLABILITY (I mean, I think it’s a word) tied in nicely with the next presentation…

Compound Effects

David Morrison ( blog | twitter ) followed up with his presentation on “Query Plan Deep Dives” (I had seen this at SQL Bits, but it’s a great session so I had no problems watching it again) and, as an aside, through his presentation he showed us the compound effects that can happen from not specifying a columns NULLABILITY (it’s got letters so it’s word-like…)

Now his slides and scripts are up on his blog and they do a great job of walking you through them so check them out and you’ll see the compound effects they create!

Here’s a little teaser…


-- now I want all people who's email isn't in the email table
SELECT /*C.FirstName ,
    C.LastName ,*/
    C.EmailAddress
FROM dbo.Contact AS C
WHERE C.EmailAddress NOT IN (SELECT E.EmailAddress
                             FROM dbo.Emails AS E)

GO

Consequences

Which brings us back around to consequences or as I like to put it “How I Pissed Off A Dev By Refusing A Simple Request”.

To be quite honest, it was a simple request. A requirement came in to expand a column datatype up to varchar(100), so one of devs wrote up a simple script and passed it onto the DBAs to check as part of the change control procedure.

ALTER TABLE tablename
ALTER COLUMN columnname varchar(100)

And I said no.

“WHY???!!!“, you may shout at me (he certainly did), but I’m going to say to you what I said to him. “Give me a chance to explain before you take my head off, alright?”

While there is nothing wrong with the above code syntactically (is that a word?) but I couldn’t approve it since that column was originally NOT NULL and the above script would have stripped the column of that attribute! Business requirements dictated that it should not allow NULLS, and hey, who are we to argue with that 😐

Double checking to see if the column is NULL or NOT NULL allowed me to see a problem with that code, one that many people would consider simple enough to just allow it through at a quick glance. Which could have opened up problems further down the line if it had run…

Thanks to the User Group, I now know that it could have a knock on effect with our query plans as well!

ALTER TABLE tablename
ALTER COLUMN columnname varchar(100) NOT NULL

There, that’s better!

DBAs deal with databases and consequences

DBAs get a lot of stick sometime, the “Default Blame Acceptors” or the “Don’t Bother Asking” but a lot of the time, it’s not that we want to say no, it’s just that we have to take into consideration a thousand little things that could snowball into 1 giant problem.

With the rise of DevOps, check out the latest T-SQL Tuesday, DBAs have gone from going

“No”

to somewhere along the lines of

“Not this second, let me check it out and see what we can do”

If pressed further, we may rely on the good, old “it depends” though. Hey, clichés are there for a reason; they work!

It just goes to show that, like the IT profession, DBAs are constantly evolving.
Continuosly learning, checking out new helping technologies, and going to User Groups are going to help us to deal with it.

Just remember, in the end,

P.S. I should probably mention that the Nicolas Cage memes are because of this blog post by Nate Johnson ( blog ) that I enjoyed so much that I had to do something in response. I’m not normally this crazy, I swear!

Keeping New Lines in SQL Server.

Where I compare scripts to BBQ because of course I would 😐

I have this personal opinion that one sign of a good DBA is their ability to automate things and, before the DBA world found PowerShell, the way to do this was with T-SQL.

For example, a T-SQL script to get permissions assigned to a database principal could also include a column to REVOKE those permissions. This could be “automated” with some dynamic SQL.

SELECT dprin.name AS DatabasePrincipalName,
       OBJECT_NAME(dperm.major_id) AS ObjectName,
       dperm.permission_name AS PermissionName,
       N'REVOKE '
         + dperm.permission_name
         + N' ON OBJECT::'
         + OBJECT_NAME(dperm.major_id)
         + N' FROM '
         + dprin.name COLLATE Latin1_General_CI_AS AS RevokeMe
FROM sys.database_permissions AS dperm
INNER JOIN sys.database_principals AS dprin
  ON dperm.grantee_principal_id = dprin.principal_id
WHERE dprin.name = 'public';

RevokePermissions — This can be improved A WHOLE LOT…

What about if we want to improve this?

This is nice but what about if we are ~~paranoid~~ forward-thinking enough to realize that this could cause us problems?

“How?” You ask. Well what happens if there existed another database, say [NeedsAllPermissions], with the same table name and the same login has permissions on it.

Are you going to revoke permissions from that database? It needs ALL of them! It says so in the name!

So in an effort to not shoot ourselves in the foot, we add in the database name to our revoke script.

SELECT dprin.name AS DatabasePrincipalName,
       OBJECT_NAME(dperm.major_id) AS ObjectName,
       dperm.permission_name AS PermissionName,
       N'USE '
         + DB_NAME()
         + 'GO'
         + N'REVOKE '
         + dperm.permission_name
         + N' ON OBJECT::'
         + OBJECT_NAME(dperm.major_id)
         + N' FROM '
         + dprin.name COLLATE Latin1_General_CI_AS AS RevokeMe
FROM sys.database_permissions AS dperm
INNER JOIN sys.database_principals AS dprin
  ON dperm.grantee_principal_id = dprin.principal_id
WHERE dprin.name = 'public';

Yes, we’re only using our database now!

So all is well with the world…

Until the day comes when you actually want to revoke permissions to that user. So you run the above code, copy the RevokeMe column and paste it into the management window. and you get…

GO is a special little guy. It’s not exactly T-SQL. It’s a way of telling the SQL Server Management Studio (SSMS) to send everything before it, from the beginning of the script or the preceding GO, to the SQL Server instance.

If you read the documents, the main point to take away is…

A Transact-SQL statement cannot occupy the same line as a GO command. However, the line can contain comments.

GO is a special little snowflake and needs to be on his own line then. Simple enough if you know that SQL Server converts CHAR(10) into a New Line.

If you didn’t know that, well you know that now….P.S. CHAR(13) is a carriage return 😉

So let’s update our script with some CHAR(10) and see what happens then.

SQL & BBQ, both work well with CHAR

SELECT dprin.name AS DatabasePrincipalName,
       OBJECT_NAME(dperm.major_id) AS ObjectName,
       dperm.permission_name AS PermissionName,
       N'USE '
         + DB_NAME()
         + CHAR(10)
         + 'GO'
         + CHAR(10)
         + N'REVOKE '
         + dperm.permission_name
         + N' ON OBJECT::'
         + OBJECT_NAME(dperm.major_id)
         + N' FROM '
         + dprin.name COLLATE Latin1_General_CI_AS AS RevokeMe
FROM sys.database_permissions AS dperm
INNER JOIN sys.database_principals AS dprin
  ON dperm.grantee_principal_id = dprin.principal_id
WHERE dprin.name = 'public';

WithDBAndChar10 — That smokey, wood-fire CHAR

Now, when we paste the RevokeMe column to a new window, we get…

StillNoNewLine — Oh look, it’s a wild, rare nothing…I love them!

…absolutely no difference. 🙂

Why am I smiling?

Here, around 500 words in, we get to the meat of our post. How do we keep new lines when copying in SQL Server?

Tools | Options | Query Results | Results to Grid | Retain CR/LF on copy or save

Two things need to be done here.

This checkbox needs to be enabled.
CHECK!
A new window needs to be opened and used.

New window open, we run our script again, and this time, when we copy and paste the results, we get…

FinallyWorks — Winner, Winner, BBQ Chicken Dinner

Dessert:

So if you are using T-SQL to create scripts, and you’re having this problem with GO or just new lines in general, make sure that the “retain CR/LF on copy and save” checkbox is ticked.

Now, improve that script more, throw it in a stored procedure, and you never know, it may be semi-useful. 🙂

SQL Prompt: For Your Group By Problems

I’m going to point people to this that have “My Group By isn’t working” questions…

The Joys of SQL:

Did you know that the SQL language allows you to do amazing analysis of data such as aggregate functions?

SELECT t.session_id,
       t.request_id,
       SUM(t.user_objects_alloc_page_count) AS UserObjectAllocated,
       SUM(t.user_objects_dealloc_page_count) AS UserObjectDeallocated
FROM sys.dm_db_task_space_usage AS t
GROUP BY t.session_id,
         t.request_id;

The Pains of SQL:

But…if you forget to put in the GROUP BY clause, as a ski instructor once said, you’re going to have a bad time!

Need Group By — Pizza…French Fries…Pizza

The Repetitiveness of Questioners:

So some eager yet lost scholar ventures into this land of aggregate functions, reads the error message and adds in a GROUP BY clause.

SELECT t.session_id,
       t.request_id,
       SUM(t.user_objects_alloc_page_count) AS UserObjectAllocated,
       SUM(t.user_objects_dealloc_page_count) AS UserObjectDeallocated
FROM sys.dm_db_task_space_usage AS t
GROUP BY t.session_id;

Now don’t scoff, this happens. I mean the error message is still red, looks nearly identical to the original one encountered, and can cause a rage-inducing damnation of SQL Server error messages.

The Enlightenment of Questioners:

Trawling the bulletin boards, question sites, and forums – okay maybe a quick question online, it’s called poetic exaggeration people! – they eventually learn the folly of their ways and correct their mistake.

SELECT t.session_id,
       t.request_id,
       SUM(t.user_objects_alloc_page_count) AS UserObjectAllocated,
       SUM(t.user_objects_dealloc_page_count) AS UserObjectDeallocated
FROM sys.dm_db_task_space_usage AS t
GROUP BY t.session_id,
         t.request_id;

The Euphoria of SQL Prompt:

Now I consider myself lucky that work has invested in the RedGate tools, and right now, especially SQL Prompt.

I’m not going to talk about “Save and Recover Lost Tabs” – saved my ass many times.
I’m not going to talk about “Code Formatting” – saved my sanity many times.
I’m going to talk about “Autocomplete”.

A well-known secret with SQL Prompt’s autocomplete is the snippets feature. With this, you can increase your productivity by 75% from typing out G R O U P [space] B Y and instead use gb and hit tab.

The Ecstasy of SQL Prompt:

Do not get me wrong, a 75% increase in productivity? I’ll take that!

That is a well-known secret though, and it’s slightly hard to get excited about a well-known secret.

However, what if I told you that SQL Prompt had another lesser-known secret that can increase your productivity and ensure that you do not forgot to add the necessary columns to your GROUP BY clause?

Interested? Ah c’mon!
You sure you’re not interested?…. That’s better!

So first of all, let us increase the number of non-aggregated columns in our SELECT to include database_id, is_remote_work, and exec_context_id. Including our session_id and request_id these are all columns that we are going to need to add to our GROUP BY clause, because…well…business logic.

Only problem is ain’t nobody got time for that.
SQL Prompt knows this and adds the following little snippet after a GROUP BY autocomplete.

Shortcut shortcut — Whoa! Whoa! You can **deliver** Pizza to me?

Hitting tab on that includes everything in the SELECT that is not part of an aggregate function, leaving us to concern ourselves with loftier things…

Final Works — Like whatever happened to Pizza in 30 mins or free?

Pizza:

Now I don’t work for ~~pizza~~ RedGate, I’m not affiliated with them, and I don’t get any money off of them. In fact, I’d say that they’d happily pay me not to write about them but when I found this autocomplete feature, I got too happy not to share it!

So save yourself the trouble of typing everything out and spare yourself the pain of error messages.

Use this lesser-known secret and have more time for pizza.

Don’t talk to me about it!

Shall I Compare Thee to Another Table?

Compare-SqlTableColumns

Thou hast less columns than thine brother…

It’s not just Indexes

Default to on

Do I like this?

The Set-Up:

Create Table:

Old, Way WHERE old=way

New JOIN Way ON new = way

Dynamically?

Explain it to me.

Full Dynamic Script

Summary:

If you’re going to do it…

…do it Pivot

Stats:

Execution Plan:

..do it UNION

Stats:

Execution Plan:

…do it PowerShell

Get-Results

Get-Stats:

help *execution*; help *plan*

Finishing off

User Groups are great, aren’t they?

The Chaos Theory

Compound Effects

Consequences

DBAs deal with databases and consequences

What about if we want to improve this?

So all is well with the world…

SQL & BBQ, both work well with CHAR

Why am I smiling?

Dessert:

The Joys of SQL:

The Pains of SQL:

The Repetitiveness of Questioners:

The Enlightenment of Questioners:

The Euphoria of SQL Prompt:

The Ecstasy of SQL Prompt:

Pizza:

help execution; help plan