We’re on quite a roll with window functions these past few weeks. Last week we looked at the operators we’d see in execution plans when using a window function. This week I wanted to tackle one of the more troublesome ones specifically: the Sort operator. We know that sort operators are expensive in our queries. To use […]
After last week’s post I got to thinking that although we’ve looked at how to implement window functions, we haven’t peeked under the hood to see how they are executed. Then what do you know, Kevin has picked up my post to provide an alternative approach. He observed that whilst his approach was more straightforward it produced a more […]
We revisited window functions last week for T-SQL Tuesday. As we’re in that area there’s another example I thought was worth exploring. Can we group data whilst applying window functions in the same query? The problem For our example we’ll use the same sample data as last week. This contains sales values broken down by period, also […]
This month’s invitation from Steve asks us to about how window functions have made life easier for us. Before we get into that let’s have a brief recap of what window functions are for those who aren’t familiar. What are they? Window functions are like regular functions we’d use in a result set such as SUM() or MIN() but more […]
When processing data there is frequently a need to rank the outputs. This could be to limit a selection of records to return, or provide a type of leader-board for reporting. There are a number of ranking functions within the SQL language which we’ll look at here with examples and outputs. We’ll start with some […]
After recently covering window functions I thought it would be a good opportunity to share one of my favourite use cases for them. The functions for ranking and aggregations have their own clear use cases but here I’d like to discuss a particular use for the LAG and LEAD functions. The scenario There are instances […]
In the previous posts we covered the ranking and aggregate window functions and this time we’ll be finishing the series covering the Analytic functions, seeing what an alternative to Window Functions might look like, and then wrapping up what we’ve covered in this series of posts. As with our previous examples we’ll set up our […]
Last time out we talked about the Ranking options which are available for Window Functions. This time we’ll be covering the Aggregate options which are available to us with them. We’ll also introduce a new feature to see how we can limit the rows the function is performed on, but different to the PARTITION method. […]
Introduction Window Functions in SQL Server are functions which can be applied in the SELECT portion of a statement and will return a value relative to other records in the same data set. These functions differ from standard functions such as aggregates where those would combine multiple records together to come up with a result […]
Andy Brownsword 