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Inserts, updates and deletes on large tables can be very slow and expensive, cause locking and blocking, and even fill up the transaction log. One of the main benefits of table partitioning is that you can speed up loading and archiving of data by using partition switching.
Partition switching moves entire partitions between tables almost instantly. It is extremely fast because it is a metadata-only operation that updates the location of the data, no data is physically moved. New data can be loaded to separate tables and then switched in, old data can be switched out to separate tables and then archived or purged. All data preparation and manipulation can be done in separate tables without affecting the partitioned table.
T-SQL Tuesday #65 is hosted by Mike Donnelly (@SQLMD). There is no specific topic to write about this month, Mike simply wants us to learn something new and then write a blog post to teach it to others. I want to share something that I only recently learned, something I wish I had known about years ago, something that became part of my toolbox as soon as I discovered it: the Numbers Table. It is so simple and solves so many problems that everyone should know about it :)
A Numbers Table (perhaps most known as a Tally Table, sometimes called an Auxiliary Table of Numbers and even referred to as the Swiss Army Knife of SQL Server) is a one-column helper table that contains the numbers 1, 2, 3, 4, 5 and so on all the way up to the-highest-number-you-could-possibly-need.
It can be used to replace slower loops and row-by-row operations with faster set-based operations, generate dates, split strings, find gaps in data sets, expand data sets, insert test data and probably hundreds of other things. There are so many great and detailed articles already published about this topic, so I will stick to the T-SQL Tuesday topic of “Teach Something New” and share the two most recent things I learned: different ways to create a numbers table, and different ways to quickly insert test data by using a numbers table.
There are many benefits of partitioning large tables. You can speed up loading and archiving of data, you can perform maintenance operations on individual partitions instead of the whole table, and you may be able to improve query performance. However, implementing table partitioning is not a trivial task and you need a good understanding of how it works to implement and use it correctly.
Being a business intelligence and data warehouse developer, not a DBA, it took me a while to understand table partitioning. I had to read a lot, get plenty of hands-on experience and make some mistakes along the way. (The illustration to the left is my Table Partitioning Cheat Sheet.) One of my favorite ways to learn something is to figure out how to explain it to others, so I recently did a webinar about table partitioning. I wanted to follow that up with focused blog posts that included answers to questions I received during the webinar. This post covers the basics of partitioned tables, partition columns, partition functions and partition schemes.
Pragmatic Works hosts and records free webinars every Tuesday and Thursday, called Free Training on the T’s. In March 2015 they wanted to highlight Women in Tech (WIT) by hosting nine webinars with speakers from the SQL Server community. I was very honored and excited to be invited, and a little nervous since it was my first ever webinar.
The introduction was not included in the recording, but it can be summed up as “thank you to Pragmatic Works for supporting WIT, thank you for attending my webinar, my name is Cathrine and this is an introduction to table partitioning” :) There were some technical issues so the sound is missing for about a minute in the middle of the webinar, and I couldn’t see any questions in the chat. To all of you who asked questions, I’m sorry for not answering during the webinar, but I have now received the transcript and will answer your questions in upcoming blog posts.
Upcoming blog posts Ed Leighton-Dick (@eleightondick) recently announced a #SQLNewBlogger challenge where those who participate will write one blog post every week in April. I have decided to participate in this challenge, and I encourage everyone else to do the same! :) I got a lot of great questions during my webinar that I want to answer in more detail with scripts, step-by-step instructions and pictures, so I have picked Table Partitioning as my topic for the challenge. You can find all the blog posts in the Table Partitioning in SQL Server Archive, and check back every week in April if you want to learn more about Table Partitioning basics! :)
Preparing for the exam
My plan was to work my way through each chapter in the Training Kit book. I read each chapter and answered the quick check questions, lesson review questions, and case scenarios out loud to myself. I did all the exercises, but none of the suggested practices. Instead, I tried to use what I had learned at work. For example, I rewrote some of our queries to use the new window functions, and it was easier to understand how FOR XML worked when I queried data I was already familiar with.