Date handling in SQL Server tends to accumulate tried and trusted combinations of DATEPART(), DATEADD(), and DATEDIFF() – with nested variations. The challenge with these isn’t raw performance, but more with conveying intent and readability. So let’s look at some simpler patterns to try and avoid some of these and be clearer with what we’re […]
Computed columns allow us to bake logic into our schema. I find particular use for these when reviewing or optimising established solutions where you spot the quirky ways the data is being used. Here I want to demonstrate 3 symptoms and show how different implementations of computed columns solve them. Baking the expression Common expressions […]
For the bicentennial edition of T-SQL Tuesday, Brent has thrown down the topic of “When I’m looking at a query, I bet it’s bad if I see ____.”. I’m expecting the Brits out in force for this game of Blankety Blank. There are some things which terrify me when troubleshooting: Not necessarily in that order. But there’s […]
Last week I demonstrated a fast binary search approach to quickly slice through large unindexed tables. I love the approach, but it fell short in two key areas – drop-in usage, and proper boundary handling. Why Let’s recap what we’re doing here: Large append-heavy tables – like logs or audits – often don’t have a useful index […]
I know, clickbait right? Hear me out. Searching vast log or audit tables without indexes is painful. Narrowing down a specific time range often means scanning millions or billions of rows. But that doesn’t have to be the case. Approach This approach is designed for tables with two particular characteristics: The combination of these characteristics […]
I don’t use RAISERROR often – I usually forget which severity code to use. After looking at a sprinkling of them recently I decided it was time for a refresher, so come along for the ride. If you check out the online documentation it states that “New applications should use THROW instead”. It also sounds like its used to raise […]
When reviewing our execution plans we’ll see joins executed using different operators. The type of operator is chosen based on the data that’s available to join and how the optimiser wants to execute it. In this post we’ll take a look at what the operators are, when they are used, and how they work. These […]
Sometimes you want to segment records. It may be splitting a customer base for marketing purposes, or segmenting a user base for a new feature. Good segmentation makes clean divisions in the data. In this post we’ll see a way to achieve that with a great deal of help from Window Functions. This post was […]
Implicit conversion happens in SQL Server when the engine detects a mismatch in data types and automatically converts from one type to another. This can be helpful as it makes different types interchangeable and is generally transparent to the client, but it can come with issues. Usually the downside from implicit conversion is seen through […]
The UNION and UNION ALL operators allow us to combine results, but there’s no guarantee that each set of results uses the same data types. So what data types are returned? For the longest time I thought the data types from the first set of results were used for the final results. That’s not the case. Understanding how this […]
Andy Brownsword 