Database Engineering: Database Modelling: Do I need to have an incrementing identity int/bigint as my clustered index in a SQL Server database?

When you want to produce a professional table design that will scale in the future and stop you being called at 4 AM to fix a performance issue, will you regret that decision to not add an incrementing “id” column to that core table?

When you look in forums, do you see people fiercely guarding their opinion that you should/should not include an id column?

If you have a PIVOT query and it isn’t returning the data you expect, what can you do to troubleshoot it? The thing to do is to break it down into the constituent parts. First, lets take a look at a query and see what we can do to help.

If you have this query:

SELECT [1] AS Student1, [2] AS Student2, coalesce([3], 0) AS Student3
FROM 
    (SELECT student_id, amount FROM [a]) as source
    PIVOT (
            SUM(amount) FOR student_id in ([1],[2],[3])
        ) as pv

Step 1 - Do you have any actual data?

If we break this down, the first thing is we select the original data from the table here:

How to delete data efficiently

When we delete data from a table in SQL Server, we can often find that the delete is slower than even the original insert, especially if the insert was made using the bulk insert API. Often when people find that they have a delete that is taking longer than it should and blocking other users, they kill the delete, but the rollback takes just as long if not longer than the delete up until that point. They can sometimes panic and restart SQL Server, but when the server starts back up again, it puts the database into recovery mode and continues rolling back that data.

How do you know whether a database code change is going to be great, okay or awful? If you want to test a new version of SQL Server how do you know whether to leave on or disable the legacy cardinality estimator? Will the latest cumulative update destroy the performance of your application?

You don’t have to wait until production to know if the change you are going to do works or not and building a system to test the performance of your database is probably more straightforward than you realize.

Reading Time: 5 minutes (just do it!)

There is a lot of confusion when it comes to designing tables in SQL Server around whether to pluralize names or not. How do you choose whether to pluralize or not?

If we want to store a list of people and their details do we use “Person”, “Persons”, “People” or “Peoples”? Some people will use “People” and some will use “Person”, other persons or people would go for “Peoples” or “Persons”.

Reading Time: 15 minutes (it is quite hard going, but you need to know this if you need to work with the DacFx)

DacFx - Getting the data type of a column on a table, a rehash of an old blog post

This post has been years in the making, I did a version of it years ago here: https://sqlserverfunctions.wordpress.com/2014/09/27/querying-the-dacfx-api-getting-column-type-information - well fast forward 5 years to now and I can now understand how it works and whereas before I basically sat in a debugger trying to figure out what method to use. I am now pretty confident I can get to any property I need using excel rather than using a debugger and reflection, this makes me happy :)

Reading Time: 4 minutes (not a minute longer)

TLDR;

You probably don’t want to actually merge dacpac’s you probably want to deploy multiple and use /p:IncludeCompositeObjects=true.

If you do really want to merge dacpacs you can start with this sample: https://github.com/GoEddie/DacpacMerge

Why?

I was reading the dacfx issues on the dacextensions sample’s github site: https://github.com/Microsoft/DACExtensions/issues and one of the issues https://github.com/Microsoft/DACExtensions/issues/23 asked about how to merge dacpac’s and I have been asked a few times how to do this and I thought there was a sample but I couldn’t find it so I knocked a quick one up.

Over the last couple of years I have been using VSCode more and more and Visual Studio less and less, this is great but there isn’t first class support for SSDT in VSCode, it would be great if there was but there isn’t today. This means I need to use Visual Studio to work with SSDT but often I find I just need to change a stored procedure or table and I don’t actually need the full SSDT experience, just a subset - can I change something and does it build, and can I deploy that build and run the tests?

Sometimes you don’t have the perfect development environment for SQL Server, sometimes you deploy to things like SQL Azure and want to test locally, for various reasons it is possible that you want to deploy to one version of SQL Server but set the project properties to a different version of SQL Server. If you find yourself in this situation you might need to use the parameter AllowIncompatiblePlatform which essentially says “I know I said the project is for SQL 2017 but I am deploying to SQL 2014”, anytime you say this you also sign the contract that says “If I am deploying to a lower version then I have made sure I haven’t used any keywords or object types that didn’t exist in that version and also if everything fails then so be it, I live with my choices every day”.

I have been asked a few times now for course completion certificates so I have decided to give out certificates to anyone who pays for a plan and sends me a screen shot of a unit test they have written and answer a question on unit testing.

I will generate the certificates by hand so i’m not doing them for everyone otherwise I would have hundreds to do (over 300 people have now taken the online self-paced course).