Sql-Server

Working with dates and times in database systems and programming languages has always been “interesting”, at least interesting in the sense that the old Chinese curse meant when it said “may you live in interesting times”.

One of the curious variations though is the use of Julian day numbers. It’s a count of the number of days since the beginning of the Julian period: https://en.wikipedia.org/wiki/Julian_day

SQL Server doesn’t currently have a built-in function for converting to or from these so we added functions to our free SDU Tools for developers and DBAs. You can use the functions directly from our tool kit, or use them as examples of how to write these functions.

2018-03-28

The CREATE INDEX statement is used to do exactly what its name says, it creates an index. But when you say CREATE UNIQUE INDEX, you are doing more than that; you are enforcing a business rule that involves uniqueness.

I have a simple rule on this. Wherever possible business rules like uniqueness, check values, etc. should be part of the design of the table, and not enforced in an external object like an index.

2018-03-27

There are a number of words related to SQL Server that are overloaded. One of those is “mirroring”.

Mirroring backups has nothing to do with other concepts like database mirroring.

Mirroring backups allow SQL Server to send the same backup to more than one location at the same time. The Books Online page for the BACKUP command describes the clause this way:

“MIRROR TO <backup_device> [ ,…n ] Specifies a set of up to three secondary backup devices, each of which mirrors the backups devices specified in the TO clause. The MIRROR TO clause must specify the same type and number of the backup devices as the TO clause. The maximum number of MIRROR TO clauses is three.”

2018-03-26

I was asked a curious question the other day: “Are all changes made to production systems actually deployments?”

I wish the answer was yes, but unfortunately patches do get applied directly to production systems without going through standard deployment processes.

Everyone understands the scenario. Code has been deployed using the normal processes, then someone has something that simply must be fixed urgently in the productions systems. At that point, you have two choices:

2018-03-23

I started working with SQL Server in 1992, but all through the 1980’s and 1990’s, I was also working with Progress 4GL. I thought it was the best of the character-based 4GLs but unfortunately, they did a poor job of migrating to Windows and we decided to stop using the product.

One thing that I used to love with Progress though is that the metadata for each column in the database was much richer than what is present in SQL Server. In fact, Microsoft Access was probably closer to it in that regard. It’s something I really missed when moving to SQL Server. In Progress, when I defined a column, I could also define things like:

2018-03-22

Some of the simpler tools that we’ve added to our free SDU Tools collection over the last year or so, have turned out to be quite useful.

A good example of this is CountWords.

This function takes a T-SQL string, removes the punctuation, excess whitespace, etc. and then counts the number of words contained. There are a few things that can still trick it (avoiding that would need very detailed langauge parsing) but it’s quite good.

2018-03-21

Recently, I posted a link to show how to turn on ANSI_NULLS for  a table. It’s not normally easy to change that but we added a procedure to our free SDU Tools to make it easy.

But one of the comments I received was a question basically saying “OK, you’ve shown how to change it but you haven’t mentioned why it matters in the first place”.

Fair enough. So that’s the topic of today’s post.

2018-03-19

I had a previous life as a developer and ran a software-development house. Even then, I was very focussed on data. I don’t think I’ve ever had a BD (before data) period. I see almost everything I’ve ever worked on in data-related terms, so perhaps it’s the time before I focussed on data.

But what this does mean is that whenever I get together with other data-related people, I’m one of the people who is asking why things that are taken for granted in the developer community, aren’t present in SQL Server and its T-SQL language.

2018-03-16

I’ve mentioned in an earlier article about scripting multiple objects at once, how useful the Object Explorer Details window is, and how little understood it is.

Another useful option in it, is that the displayed columns can be changed. In particular, you can add columns that would be useful. Let’s look at an example.

In Object Explorer, I’ve expanded the WideWorldImporters database and clicked on the word Tables:

Next, I hit the F7 key, and the Object Explorer Details pane opens showing this:

2018-03-15

When you create script out a table in SQL Server using SQL Server Management Studio, you’ll notice that it scripts more than just the table itself. Before the table, it scripts the values for ANSI_NULLS and QUOTED_IDENTIFIER.

A common problem that I see is that someone highlights the CREATE TABLE statement and runs it, without highlighting the SET options above it. That has the chance of leading to the wrong values. I don’t run into big issues with QUOTED_IDENTIFIER but I certainly run into issues with ANSI_NULLS.

2018-03-14