Sql-Server

When you work with Azure SQL Database, you’ll quickly learn that you send queries to a single database, and you can’t execute USE statements to change to another database. Importantly, you also can’t use four-part names to access objects in other databases like this:

ServerName.DatabaseName.SchemaName.ObjectName

So it’s not surprising that when I’ve been reading some questions in Stack Overflow, asking how on earth you can join the list of users in your database, to the list of logins in the master database. And less surprising that the answer normally is that you can’t do that, and you need to connect to each separately. However, that’s not true. You can get to them using external tables. Let me show you how:

2019-09-17

When you store data in a database,  individual values are stored in columns. Now columns have 2 basic characteristics:

• Data type
• Nullability

Another common characteristic is:

• Size (can be maximum length, precision, scale, etc.)

The first of these, the data type of the column, determines what types of value can be stored in the column. For example, I might have an email address and I might decide that that is a string of characters, but I might also have a price and might decide that that needs to be a number of some type.

2019-09-16

Security in Snowflake is quite different to what’s implemented in SQL Server.

In SQL Server, objects have owners that can either be specific people, or as occurs when a dbo person creates an object, it is owned by the dbo role. In Snowflake, objects in the database also have owners, but the owners can’t be users, they are always roles.

When you create a database, there are four pre-defined roles:

2019-09-13

I wrote last week about how I don’t like unnecessary abbreviations. It’s all part of a desire to see higher quality code, because that costs less to maintain and support.

Another key issue that troubles me in development is when I see inconsistency.

Single Brain

When you have a team of people doing work, you need to endlessly try to make the outcome look like it’s come from a single brain. And equally importantly, make it look like it’s come from a single brain that cares about quality and attention to detail.

2019-09-12

Every now and again, I need to store IP address values in T-SQL and I want to check if the string that I’m passed is a valid IP address. So, in our free SDU Tools for developers and DBAs, we added a simple tool that works that out. It’s called IsIPv4Address.

You can tell by the name that it only works with IPv4 addresses, not IPv6.

Nothing complex. It takes a string, checks the format, and the range of octet values, and returns its verdict.

2019-09-11

While it might be obvious that it’s important to format your T-SQL code for readability, it might be less obvious that there’s no agreed standard for how to format that code.

Everybody has their own style. The main thing. People will tell you all the time is just to be consistent. But then they’ll tell you they don’t like the format you’ve used.

Take a reasonable style and then to just keep applying it.

2019-09-09

Like most products, Snowflake comes in a number of editions, and you can see the current editions in the main image above. (Keep in mind that they could always change at any time and to check their site for the current options).

First thing I need to say is that I really like the way that most of the SQL code surface is pretty much identical across editions. I wish that was complete coverage but it currently doesn’t include materialized views.

2019-09-06

There’s an old joke in computing about how you can spend 90% of the time on a project working out what to name things, and end up without time for doing the work.

Phil Karlton is credited with having said: There are only two hard problems in Computer Science: cache invalidation and naming things.

I really liked Jeff Atwood’s or Leon Bambrick’s update though: There are two hard things in computer science: cache invalidation, naming things, and off-by-one errors. (Can’t work out who said it first).

2019-09-05

I regularly run into situations where I need to execute a T-SQL command in each database on a server. The built-in Microsoft method is to call the unsupported sp_MSforeachdb, and there have been other methods over the years. None of them really worked the way that I wanted them to, so in our free SDU Tools for developers and DBAs, we added a tool that does just that. It’s called ExecuteCommandInEachDB.

2019-09-04

It’s really important when you’re writing SQL Server code (or T-SQL in particular) that you add comments to the code where something isn’t obvious to someone who’s reading it.

Here’s an example of comments being used:

There are two ways that comments can be added:

If you put a double-dash on a line, anything after it is a comment.

If you need to comment a block of code, you can put a /* to start the comment and */ to end it. I’m not a fan of block comments in T-SQL because you can’t nest one comment inside another comment. With the double-dash method, that’s not a problem.

2019-09-02