The Bit Bucket

I might be somewhat anal when it comes to database design. (Probably almost any type of coding). Perhaps it’s a mild form of OCPD-behavior, but inconsistency frustrates me. (I’m told that OCPD is the correct term, and that people often apply OCD to that behavior incorrectly).

Worse, inconsistency leads to nasty, hard-to-find errors and your applications become more and more fragile.

If I’m holding an email address and I define it as 70 characters in one place, 100 in another, and 160 in yet another, I have the chance of random failures when I’m moving data around or assigning values from place to place. (For email addresses, I recently discussed why they should be 320 characters anyway).

2017-11-29

Many years back, I was invited to chair a course accreditation panel for a local TAFE (Technical and Further Education) course. They had started to offer a computing-related 3 year diploma, and the hope was that it wasn’t too far below the 3 year degrees offered at local universities. One part of that accreditation process involved me discussing the course with the staff members who were teaching it.

After talking to almost all the staff, what struck me was how similar they all were. In the requirements for the course, there was a standard that each staff member needed to meet, but there was also a requirement for the group of staff to be diverse enough to have broad knowledge of the industry. There was no individual staff member that you could identify as not being at the appropriate standard, but almost all of them had exactly the same background, career progression, etc.

2017-11-28

When designing databases, one question that comes up all the time is how large columns should be.

For numbers, the answer is always “big enough but not too big”. This week I’ve been working at a site where the client numbers were stored in int columns. Given the clients are Australians and the Australian Bureau of Statistics Population Clock says there are just under 25 million of us, an integer seems a pretty safe bet, given it can store positive numbers up over two billion. It’s hard to imagine that number being exceeded, but I’ve seen people deciding that it needs to be a bigint. I doubt that. Even if we count all our furry friends, we aren’t going to get to that requirement.

2017-11-27

I had the great pleasure to record another SQL Down Under podcast last week with the Power BI general manager Kamal Hathi.

In the show, Kamal and I discuss the current state and potential futures for Power BI, its relationship to SQL Server Reporting Services, and its development and extensibility models.

You’ll find the show here: https://podcast.sqldownunder.com

I hope you enjoy it.

Note: We had a few unexpected audio issues with the recording. Sorry about that. We’ll do better next time :-) It’s still pretty good and I’ll still think you’ll find it interesting.

2017-11-24

Everyone working with databases knows that having too many indexes can be a problem. Indexes need to be modified whenever the data in the associated tables need to be modified, so yes it can slow down data inserts, updates, and deletes.

How big a problem is too many indexes?

Overall, I’m not as concerned about this as many other people seem to be. I always want to focus on what the system is spending its time doing, and on most systems that I work on, that’s reading, not writing.

2017-11-24

I often see people using SQL Server Management Studio (SSMS) and doing very repetitive editing tasks that could easily be carried out by using the selection and changing of rectangular regions of code.

The simplest example of doing this is to insert a bit of text on a number of rows. Take the following code as an example:

I’ve got the skeleton of a list of columns in a CREATE TABLE statement but let’s assume that I’m a “comma in front” person and want to put a few spaces and a comma, etc. in front of each column after the second. I could just put the cursor on the InvoiceID line and type what I wanted, then do the same again on the next line. I could do it on the first line, then select and copy it, and insert it into the front of every other line. But what I should do is put the cursor in front of InvoiceID, and while holding Alt-shift, use the down arrow to select the beginning of every line, then just type what I want.

2017-11-23

This post covers another pair of useful functions that are part of the SDU Tools collection.

The first tool AsciiOnly deals with situations where you need to convert Unicode data (multi-byte data) to ASCII data (single byte). It processes each character and if it’s not in the ASCII range, it replaces the character with the value that you supply.  If your second parameter is an empty string, you’ll effectively strip out the non-ASCII characters, but your replacement can also be one or more characters.

2017-11-22

I work with data. I understand that for most organizations, that the data they own is the most valuable asset the company owns.

One thing I’ve learned from working with data is that unlike application software, data generally outlives generations of applications, is often used by many different applications, and typically just morphs from shape to shape over time. It almost never gets totally refreshed.

This is a good thing.

2017-11-21

Memory is a precious resource on most systems today. SQL Server loves memory, so it’s important to avoid wasting it.

One common cause of wasted memory is what we call plan cache pollution. The plan cache is the region where SQL Server stores compiled query plans (and query plan stubs).

There are some nice new DMVs that give you details of what’s in that cache but nothing still compares to one of the older compatibility views sys.syscacheobjects. You can use it to see what’s in your plan cache:

2017-11-20

SQL Server 2012 added the function EOMONTH. It returns the end of the month. That’s useful but there are two things that bug me about it:

First: What’s with the name? Do we really have to save 3 characters from ENDOFMONTH, particularly when the same version added functions like DATETIMEOFFSETFROMPARTS? When I asked, I was told it was the name of the function in Excel. I can’t admit to being happy that SQL Server and T-SQL is following the naming of a function that someone added to Excel in the 1980’s in some adhoc way.

2017-11-17