Sql-Server

This is part 4 in a series of posts:

• Part 1 covered being sure there is a locking and blocking issue
• Part 2 covered the impact of RCSI
• Part 3 looked at the impacts of indexing on locking and blocking

Today, though, I want to look at the next potential issue, and that’s deadlocks.

Deadlocks

I often hear people interchangeably using the words lock, block, and deadlock.

Locks are a standard feature of systems that are designed for concurrency. Nothing nasty to see here. When they become a problem is in two situations:

2019-05-09

A while back I wanted to do some testing of Azure Database for PostgreSQL and I needed a database to work with. So I thought I’d try to migrate a basic WideWorldImporters database across to PostgreSQL.

I wrote scripts to do the main migration but then decided that I wanted to change the names of the columns.  While a large number of people use PascalCased names in SQL Server, it’s really, really common to use snake_cased names in PostgreSQL. Object names in PostgreSQL are also limited to 63 characters. I needed to alter these names while generating the scripts and I didn’t want to do that manually.

2019-05-08

Who moved my cheese (diagram tool)?

I was part of an interesting email chain today. It started with a guy complaining that in SQL Server Management Studio 18x, the database diagram tool had been removed.

Now I was disappointed to see the tool gone. Mind you, I didn’t ever think it was a great diagramming tool. I would have hoped they might have replaced it by a better one instead of just removing it.

2019-05-07

When you run a query against SQL Server, you might want the rows to be returned in a specific order. However, the first thing you should ask yourself is whether that’s needed at all.

Sorting can be a very expensive operation if there is no suitable index that’s already sorted the data for you. And the question is: should SQL Server be the one doing the sorting? In many cases, the client application that’s reading the data might be a better place to do the sorting. That’s not always true but it’s worth considering. You often have way more clients than your single database server, and sorting data unnecessarily in the database server could limit your ability to scale your system to higher volumes.

2019-05-06

This is part 3 in a series of posts:

• Part 1 covered being sure there is a locking and blocking issue
• Part 2 covered the impact of RCSI

Today, though, I want to look at the next potential issue, and that’s indexing.

Indexing impacts on locking

It might seem obvious that you need to fix indexing issues in your database applications but it mightn’t be so obvious that locking is one of the main things that is affected.

2019-05-02

While doing my consulting work, I often come across Foreign Keys and Check Constraints that are not trusted. What this means is that either:

• They were created without checking existing data
• They were disabled for a period and re-enabled without re-checking the existing data

I like to see this fixed whenever possible. To make that easy, in our free SDU Tools for developers and DBAs, we added two stored procedures to help: RetrustForeignKeys and RetrustCheckConstraints.

2019-05-01

Look carefully at the following queries:

I’ve shown several examples here of what are called aliases. There are two basic types of aliases.

Column Alias

In the first query, I’ve used a column alias. I wanted to query the Description column in the dbo.Products table but I wanted the column called ProductName instead. So I follow the column with the word AS and then the name I want to use for the alias.

2019-04-29

This is part 2 in a series of posts:

• Part 1 covered being sure there is a locking and blocking issue

In part 1, I talked about pseudo locking and blocking issues that come from having queries running too long. I said that before you start fixing any locking and blocking issues, that you first need to make sure your queries are running fast. Today I want to discuss RCSI.

2019-04-25

When I’m writing utility scripts for SQL Server, I often need to make decisions or report on, details of the operating system that I’m running on. Unfortunately, SQL Server doesn’t have views that return this sort of information.

In our free SDU Tools for developers and DBAs, we added a series of views to help.

OperatingSystemConfiguration has details of OperatingSystemRelease, OperatingSystemName, ServicePackLevel, OperatingSystemSKU, OperatingSystemSKUName, and LanguageName.

OperatingSystemVersions has details of OS_Family, OS_Version, and OS_Name.

2019-04-24

We all see news articles talking about how company after company exposed private details of their clients, customers, and sometimes, even staff. In so many cases, a reasonable approach to encryption would have avoided these issues. Time and again though, I see people doing dodgy work on protecting their data; some even trying to roll their own protection.

Don’t do this!

Encryption is one of the most important yet least understood technologies in SQL Server. It’s improved so much over the years and 2019 makes it even better.

2019-04-23