While presenting recently and talking about dealing with bad Parameter Sniffing, I got the question; what happens to OPTIMIZE FOR hints when parameter sniffing is disabled? This is my favorite kind of question because the answer is simple: I don't know. Parameter Sniffing For those who don't know, parameter sniffing is when SQL Server uses the precise values passed into a query as a parameter (this means stored procedures or prepared statements) to generate an execution plan from the statistics using the value from the parameter. Most of the time, parameter sniffing is either helping you, or is not hurting you. Sometimes, parameter sniffing turns bad and hurts you quite severely. Usually, but not always, this is because you either have severely skewed data (some data is very different than the rest, lots…
[caption id="attachment_2548" align="alignleft" width="300"] Tired from all those blog posts[/caption] For my final blog post in the #gettingstarted, #iwanttohelp series, I decided to curate a set of presentations from the PASS Virtual Chapters. This content is available online. It's free. Most importantly for the person just getting started as a SQL Server data pro, it's good. I'm going to marry each of the presentations with my eleven blog posts in this series. The Importance of a Full Backup in SQL Server For this one I'm going to recommend Tim Radney's session Understanding SQL Server Backup and Restore. I know Tim personally and guarantee this is a good session. Why Is The Server Slow Jes Borland is a very close personal friend and an absolutely outstanding presenter (and person). She has…
There are a bunch of ways you could create a database clone. Backup and restore is one method. Export/Import is another. There are even third party tools that will help with that. However, each of these has a problem. It's moving all the data, not just once, but twice. You move the data when you export it and you move it again when import it (same thing with backup and restore). That makes these methods slow for larger databases. How can you create a database clone without moving the data multiple times? Don't Move the Data At All New with SQL Server 2016, expanded in SP1, and added to SQL Server 2014 SP2 is a new command, DBCC CLONEDATABASE. This is like a dream come true. The use is extremely…
Monday I got in on Sunday and chose to have a small dinner with a couple of friends, quiet, preparing. Monday was a less hectic day than the others . The Board had the morning off, although Redgate had me go and give a session at an event. Monday afternoon was one of our three in-person board meetings. The minutes will be published soon. I was responsible for running the meeting. I also presented two topics, first, and most importantly, our current financial status. Then I presented the initial set of thoughts towards some SMART goals for Global Growth, which I will share once they are further developed . Monday evening I had two events I had to attend. First, as part of the Executive Committee, I attended the kick off dinner…
SQL Cruise offers a number of unique opportunities for everyone involved, including speakers and sponsors. I've written before, several times, about the benefits of SQL Cruise. As an attendee of the cruise, you will get to sit in classes by amazing people (and me) talking about all aspects of the Data Platform. Further, you get the opportunity to sit down, for long hours, with these people and get, for want of a better description, free consulting time. What about as a speaker and a sponsor though, do we get benefits? As A Speaker Tim Ford is quite a bright fellow. He has tweaked and tuned SQL Cruise. I have been on SQL Cruise a number of times over the last five years, and it has changed radically since my first cruise…
SQL Server is a deep and complex product. There's always more to learn. For example, I had never heard of Correlated Datetime Columns. They were evidently introduced as a database option in SQL Server 2005 to help support data warehousing style queries (frequently using dates and times as join criteria or filter criteria). You can read up on the concept here from this older article from 2008 on MSDN. However, doing a search online I didn't find much else explaining how this stuff worked (one article here, that didn't break this down in a way I could easily understand). Time for me to get my learn on. The concept is simple, turning this on for your database means that dates which have a relationship, the example from MSDN uses OrderDate and…
Blog post #5 in support of Tim Ford’s (b|t) #iwanttohelp, #entrylevel. Read about it here. Saying that you should use the correct data type seems like something that should be very straight forward. Unfortunately it's very easy for things to get confusing. Let's take a simple example from AdventureWorks. If I run this query: SELECT a.ModifiedDate FROM Person.Address AS a WHERE a.AddressID = 42; The output looks like this: 2009-01-20 00:00:00.000 Normal right? You see the year, the month and the day followed by the time in hours, minutes, and seconds as a decimal. Ah, but there is an issue. This query is supposed to be for the reporting system, and the business only cares about the date that the values in the Person.Address table have been modified, so they don't want…
Blog post #4 in support of Tim Ford’s (b|t) #iwanttohelp, #entrylevel In SQL Server, in the T-SQL you use to query it, a view looks just like a table (I'm using the AdventureWorks2014 database for all these examples): SELECT * FROM Production.vProductAndDescription AS vpad; SELECT vpad.Name, vpad.Description, vpmi.Instructions FROM Production.vProductAndDescription AS vpad JOIN Production.Product AS p ON p.ProductID = vpad.ProductID JOIN Production.vProductModelInstructions AS vpmi ON vpmi.ProductModelID = p.ProductModelID WHERE vpad.ProductID = 891 AND vpad.CultureID = 'fr'; The above query actually combines two views and a table. This is what is commonly referred to as a "code smell". A code smell is a coding practice that works, but that can lead to problems. In this case, we're talking about performance problems. The performance problems when using views to join to…
It's weird being an introvert who likes to talk to people, but what can I do. I like talking to people. I have a number of upcoming trips, quite literally all over the world, that provide us with the opportunities to get together and have a chat. First, I'll be at SQL Saturday Boston (the 500th SQL Saturday event, HUZZAH!), this weekend, March 19th 2016. I'll be talking about the Query Store and I'll be doing a presentation for PASS since this is a milestone event. The first SQL Saturday event in Boston was #34, six years ago, which I helped organize. It's been quite the journey. I'm going to SQL Saturday Madison on April 9th. I'll be talking about the Query Store and how to automate your database deployments.…
Ouch. Let's start with the level set. I'm not an ETL expert. In fact, I haven't done any professional ETL work for several years. My skills are, at best, rusty. With this in mind, I knew I'd have a hard time extracting data from a local database in order to move it up to Azure SQL Data Warehouse. I expected to be fumbling and slow and to constantly feel more than a little stupid as I made one mistake after another. All of this came to pass. Yet... OMG! THAT WAS DIFFICULT! Here's how I started. I defined a bcp command for the tables I was interested in. I ensured it was working correctly, then wrote a little PowerShell script so I could supply a list of tables and get…