Category: Syntax

Chad Callihan looks at the fourth ranking window function:

Have you ever used the NTILE function? Or have you even heard of the NTILE function? It seems to be one of the lesser known, lesser used window functions in SQL Server. I’ve never come across it in the wild but maybe there are those that use it all the time. Either way, let’s have a look at what it does and how it can be used.

Click through for a demo. I definitely use it a lot less than ROW_NUMBER(), RANK(), and DENSE_RANK(), but I have used it to some good effect in the past, mostly in cases where I’ve wanted to focus on the top X% of data for an analysis.

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Greg Dodd doesn’t need no steenkin’ tables:

Sometimes you have a list of values or parameters that you’d like to run a select statement over the top of to get a result. There’s a few ways of doing this, usually I see people create a Temporary Table and insert the data. But is there an easier way?

Yes, we can select from VALUES:

The result of this is called a virtual table, and as far as other parts of the query are concerned, it’s just another table.

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Chris Johnson shares some thoughts:

This query is pretty simple, we’re wanting to return a set of data about the orders placed including the total cost of each order. However the orders in the database are split into an Orders table that holds the order level information, and an OrderLines table that holds information on each product ordered in each order, and we need that OrderLines table to get the cost.

So we write our query, and we join to the OrderLines table, and we sum the cost. But then, because we have an aggregate, we need to group by every other column we’re returning. And to me that just doesn’t look right, and it doesn’t convey the intention of the query properly.

In Chris’s simple example, I’m not sure I’d push it very much, but Chris does have a good point in terms of explaining query intent. Also, depending on how many order lines there are relative to orders (the next step in the chain for that query), aggregation in a common table expression could be faster than waiting until after the join to aggregate on all of the columns. In reality, that’s the most likely reason I’d make this change, assuming that it made a big enough performance difference. But if you take a much more complicated query of this sort, then I’d be more amenable to the argument.

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Greg Dodd tries out some new syntax:

Have you ever had 2 columns in a table that you need to select the maximum value from? Not the maximum value from each column, but the biggest value after comparing the columns?

Usually where I have this problem, I’d use a CASE statement, but there’s another way. 

I do like GREATEST() and LEAST() (or argmax/argmin if you’re used to those terms), though Greg does include how you can get the same functionality in versions prior to SQL Server 2022.

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Chris Johnson finds a language quirk:

Recently I found a quirk of T-SQL, where a group by statement was treating strings as the same if the only difference was one or more trailing spaces. So, ‘aa’ would be grouped with ‘aa ‘. I did some digging, and this is what I found.

Yeah, this isn’t just Microsoft’s T-SQL variant—it’s a standard part of SQL, as Chris notes later in the post.

My “just-so” story is that this might have been implemented to deal with CHAR(x) comparisons, such as CHAR(2) to CHAR(3). There’s no way to make that comparison unless you treat trailing spaces as irrelevant. Because we almost always use VARCHAR(x) or NVARCHAR(x), it isn’t something top of mind to most database practitioners, but there is a method to the madness.

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