Top Ten Things I Learned at SQL PASS Summit on 10/14/2011

Travel and busy-ness with my baby Destiny have prevented my posting this last installment in my list of top lessons learned at SQL PASS, but now here it is:

1. Buck Woody and Rob Farley are not only superstars in SQL technologies, they are talented as singer/songwriters too. Check out the video of the opening of the keynote session for proof. Cue it up at 00:02:27 to skip to the song. Their song was my favorite moment of the week.

2. On Wednesday I wrote that I wanted to learn more about Hadoop since it was part of a new feature of SQL Server 2012, and today I learned more about it than I really wanted to know, but the presentation by Dr. DeWitt was fascinating. Hadoop is a method of "divide and conquer" applied to massive amounts of unstructured (or more accurately loosely structured) data, the kind collected by websites such as Facebook, eBay, and Google.

3. If you add NOSPLASH after the path to SSMS executable in the shortcut properties, the application will open a few seconds faster. It does not seem like much, but it's a handy tip that I put in place right away.

4. If there are more than a couple of OR conjunctions in any given WHERE clause, using UNION ALL is probably a better approach. The query optimizer in SQL Server is much better at streamlining two or more small query conditions rather than one huge, complex one.

5. When possible, replace correlated subqueries in the SELECT clause with joins in the FROM clause. This is because the correlated subquery must execute once for every row in the main results, eliminating any optimization that is possible when the data are correlated in the FROM clause.

6. I learned how to create a "temporal snapshot fact table" for a data warehouse solution. This improves the efficiency of a "daily summary" fact table by using date ranges instead of individual days as the granularity level, ranges during which nothing changes in the data. I suspect this may come in handy when constructing fact tables for pledges and donations. It is definitely a nice concept to keep in the toolbox of report design.

7. I learned that the query optimizer can anticipate the best query plan even when part of the query statement has been "refactored" into a common table expression (CTE).

8. Thanks to Audrey Hammonds, I learned some great techniques for explaining CTEs effectively. I plan to use some of her presentation style and content ideas when I present an introduction to CTEs at SQL Saturday #96 in Washington, DC.

9. CROSS APPLY is comparable to an inner join and OUTER APPLY is comparable to a left join. In that same context, I learned that there is no difference in query efficiency to move a CROSS APPLY table valued expression into a correlated subquery within the SELECT clause. This is reassuring, since I have already made such a move with the FOR XML technique of turning row values into delimited strings.

10. Snow Crash by Neal Stephenson is a book I need to read. When Audrey referenced it in her presentation, about half the audience recognized it and praised it as a great read. She mentioned a few other books throughout her talk, but this one definitely stirred the strongest positive response.

Top Ten Things I Learned at SQL Pass on 10/13/2011

The learning continues...

1. The "AlwaysOn" feature of SQL Server 2012 greatly simplifies high availability through redundant servers and simultaneously optimizes reporting by allowing you to use secondary servers for reporting and the primary server for transaction processing. However, it is currently unknown whether or not AlwaysOn will be in any edition other than Enterprise. It seems likely that it is an Enterprise-only feature.

2. The "ColumnStore Index" feature in SQL Server 2012 could radically speed up queries against tables in the Shelby v.5 database, especially attendance history. I can't wait to try it out. I may install Denali to try it out even before the official release of 2012.

3. There is a version of SQL Server Express coming out with 2012 that can easily be embedded into applications. This could potentially be a way to simplify the distribution of Shelby v.5 for those customers who do not own a license of SQL Server Standard. I will be looking into it more back home.

4. The "Semantic Model" features of SQL Server 2012, when coupled with the "FileTable" feature make for a powerful combination, capable of doing searches for document content based not just on matching of strings but actually pairing of concepts. I was blown away by the demo. Any librarian in the world would have been salivating over the processes and results I saw.

5. Two more times in one day I was shown the fallacy of putting dates inside of a function in the WHERE clause. I will never do it again, I promise! But I also learned that datetime and smalldatetime are being depricated in SS2012, meaning that we should probably start using the other, new data types for time. I will pass that info along to our database developers.

6. I learned that by simply changing the varchar data type to nvarchar, we could be capturing special characters for names, addresses, and more, which would make the v.5 database friendlier to international users. I'm going to do some testing on this when I get home too, to verify what is happening in our db right now when someone puts special characters into the varchar fields.

7.  I need to kick the habit of not specifying the length of varchar values and others when I use them as variables. I've been snakebit by that one before, and what I learned today just reinforces that I need to specify length 100% of the time.

8.  Some people, no matter how smart they are about what you want to discuss, can just be too annoying to talk to. It's just better to bide your time and find someone who may not be as knowledgeable but who is willing to listen and to converse at a pace that matches your own.

9.  The 2013 Summit will be in Charlotte, NC. That will be much more convenient for me to attend, and I am very much looking forward to not having to adjust to a new time zone in order to participate.

10.  Making free form reports with PowerPivot data in the background is not only possible, it allows for greater control over formatting and the embedding of elements such as sparklines into the data results. Free form reports can even use slicers to control the content. The only downside is the fixed nature of the rows and columns, which is why PivotTables are so handy in the first place.

Top Ten Things Learned at SQL PASS on 10/12/2011

Wednesday is when the conference starts in earnest, and so I definitely learned more than I can summarize here, but these ten things really stood out to me. As with my first list, this is roughly chronological over the course of the day.

1. There are over 4,000 registered attendees at this event. Add in the presenters and the vendors, and you can imagine how packed the rooms are. It is good to have such a thriving community; and yet, it does strain the capacity of the venue.
2. SQL Server Code Named "Denali" has officially been named "SQL Server 2012," and is expected to be released in the first half of next year. "Crescent" has officially been named "PowerView" and will be a part of the SS2012 release, but apparently it requires the Enterprise edition. This is unfortunate, because that will put it in reach of only a couple of our Shelby Systems, Inc. customers.
3. SQL Server 2012 will provide connectors and (eventually) drivers for something called "Apache Hadoop." This is something I will need to learn more about. Apparently Hadoop is a way to consume gigantic amounts of essentially unstructured data (on the order of pedabytes) and generate meaningful output. I don't know that I'll ever need that in my current role at Shelby Systems, but it is an interesting feature.
4. I learned several things during the demos in the keynote, including: "sentiment" is now a measureable fact that can be quantified and reported on through the Microsoft Data Marketplace and the upcoming "Data Explorer"; only John Wayne has made more movies than Samuel L. Jackson.
5. Stephen Few is a name I heard multiple times with regard to optimizing report style and layout. I believe I'm going to have to look into his web site at www.perceptualedge.com and check out his books.
6. If I can get ahold of some mapping files that include the ZIP code layer (the Census Bureau is said to have some in the public domain), I should be able to get the mapping feature in Reporting Services to map down to that level. That would be much better than the current limit of reporting at the state level.
7. Satori Software (a vendor here as well as a partner with Shelby Systems, Inc.) could actually return latitude and longitude information back to the NAAddresses table if we added that to our service agreement with them. The additional licensing cost makes it unlikely that this feature would be a part of all our customer's ShelbyMAILROOM package, but it is interesting to know.
8. The inactivated slicer problem I noticed in the Excel PivotTables that are created programmatically from ShelbyQUERY is probably triggered by some option in the automated set up of the table. A manually-create OLE DB connection can use slicers just fine. It appears to have something to do with an OLAP-related setting, but I'm going to have to follow up on this more with Microsoft. Helpfully, one of the PowerPivot techs gave me his contact info and invited me to e-mail him if I couldn't pinpoint it on my own. I have to give props to the Microsoft staff here at PASS, who are as helpful as they can be.
9. I have been doing date filtering in the WHERE clauses of queries in a way that will impede the efficiency of the query, possibly adding multiple seconds of time to getting the query results.  I have to learn ways to avoid putting table columns into functions, even the DATEDIFF() function.
10. The pie chart is not an effective way of communicating comparisons in reports. Bar charts are far an away the best chart for most comparisons. Gauges too are relatively ineffective communicators. But the bullet chart is exceedingly good at communicating "KPI" style data with more context. I will have to learn how to create them in Reporting Services.

Top Ten Things I Learned at SQL PASS on 10/11/11

More lessons from the SQL PASS Summit 2011:

1. When your laptop is a block or more away, that is the point at which you will most need it urgently.
2. It is quite a good feeling to be an "alumnus" of the event and be able to help the first timers with getting where they need to be and oriented to the essentials for the best PASS experience.
3. Although the views I have built for use in the ShelbyQUERY environment of our software are helpful for simplifying query writing, they are not really "data warehouse" structures. They blend too many distinct "dimensions" of data together, and they confuse (at points) the dimension/fact dichotomy. Thus I cannot really use that work as the guideline for a data warehouse database design.
4. A dimension that is a "role playing" dimension does not have to exist as multiple instances in the data warehouse, not even as views of the different roles. If two keys in the fact table reference the same dimension for distinct purposes, it is a "role playing" dimension.
5. Pragmatic Works, a SQL consulting firm based in Jacksonville, Florida has actually designed a data warehouse solution for a large Baptist church in that state. I'm sure my jaw dropped when Brian Knight (founder of Pragmatic Works) told me this in today's precon session. How could this be, and I didn't know it?! I will be meeting with Brian at the Pragmatic Works booth later this week to find out more.
6. The topic "Building a Microsoft Business Intelligence Platform" sounds too ambitious to be effectively covered in a one-day training session because it actually is. Yes, Brian and Devin (the presenters) touched on each phase of the process, but the touches were alternately too light and too technical, leading to frustration on my part and (I suspect) on the part of others in attendance. It was often a case of lingering too long on a technical detail of the process so that the presenters rushed the remaining steps in the current topic to move on to the next.
7. Subway stores in Seattle do not stock provolone cheese and do not accept the points card that is so handy in the Subway stores in Virginia. On the other hand, they do have the caloric values of all the sandwiches and other menu items displayed on the menu.
8. There is an interesting similarity in the number of languages one must learn to be a biblical scholar and to be a SQL Server developer. To be a biblical scholar, one must learn Hebrew, Greek, Aramaic, German, and Latin (at least). To be a SQL Server developer, one must learn T-SQL, MDX, DAX, VB.net, and the proprietary "expression language" of SSIS and SSAS. And, just like the languages of Hebrew and Aramaic, they can be similar enough to be confusing when you are trying to learn them all.
9. The PASS Virtual Chapter for Business Intelligence has four to five live webinar-style presentations a month, generally over the lunch hour, and these webinars are then posted for free as recorded webinars the next day. I will definitely be joining this "chapter" of PASS to take advantage of the resources it provides and (perhaps down the road) to find a way to contribute back to the SQL community that has so helped me in my work these last couple of years.
10. There are people here at PASS who are familiar with Shelby Systems, Inc, even apart from the Pragmatic Works folks who worked with our customer in Florida. I met a man at lunch today from Houston who attends a church where the staff uses Shelby v.5. He volunteers as IT support at his church of about 1000 members. They have been users of v.5 since before the converstion to SQL Server from MS Access, and he confirmed that the move was a tremendous improvement in the stability of the database.

Top 10 Things I Learned at SQL PASS on 10/10/2011

I have the priviledge of being here in Seattle for the SQL PASS Summit conference all week, including two days of "pre-convention" all-day training topics. Today was the first day of the conference, and I wanted to continue a tradition of summarizing the top ten things I learned today at PASS. These are in roughly chronoligical order.

1. It is good to get back on a treadmill and work out, even though a four-month break means that I could only go 2.6 miles in 45 minutes instead of 3.1 miles in about 40 minutes.
2. The scuttlebutt I heard last year is true: the Paramount Hotel is indeed a great place to stay for PASS, as it is reasonably priced and only a block or so from the convention center. And most of the walk there is under covered awnings. If you are familiar with Seattle weather in October, you know this is no small fact.
3. Talking to and singing to my almost-three-month-old daugher Destiny over the phone is a pale substitute for doing those things with her in my arms, but even through the phone her baby talk can melt my heart.
4. Apparently SQL PASS Summit attendees receive a new backpack every year.
5. The Guidebook app for Android phones (and probably iPhones too) is a great tool for an event such as this conference, and it is definitely something we should consider using for the International Shelby Conference next year.
6. In SQL Server Reporting Services, if you use a "cast" function (such as CDate or CStr) on a textbox value to give it a specific data type, it opens up a large set of VB.net methods that can make working with that value much easier. This is especially true for datetime values.
7. I really need to become comfortable with creating and using stored procedures over plain Jane SQL queries and views. They offer distinct benefits, which appear to be worth the trouble of being unable to create them easily with ShelbyQUERY.
8. In Reporting Services it is possible to create code blocks that do more involved VB.net functions than can be summarized into a single one-line of code in an expression. I knew this had to be the case, but today I learned how to make that happen.
9. Using a "post back" concept in the Action property of a Reporting Services report element creates the ability to have interactive "buttons" that change the parameters of the report content; for instance, it is possible to add "slicer" style buttons to a chart or matrix report design.
10. A walk from the hotel to Starbucks to get a refreshing shaken iced tea lemonade takes just enough time to wait out a false fire alarm at the hotel and return to see the firefighters climb into the fire engine and head out.

Calculating ISO 8601 Dates in T-SQL

If you do not work with international dates much, you may never have heard of ISO 8601 and you may never need to know what I'm about to cover in this post. If so, consider yourself lucky. I am not so lucky. I have been called upon to design a few queries for international customers of Shelby Systems, and in a few cases the queries have required temporal (i.e. time-related) analysis based on the ISO 8601 standard. And although I was not lucky enough to avoid the task of working with ISO 8601 in SQL, I have learned quite a bit about temporal querying in the process, so what I have lacked in luck I have made up for in knowledge. I see that as a fair trade.

In brief, ISO 8601 is a set of rules standardizing the representation of dates and times to facilitate international commerce and communication. For an comprehensive discussion of the full ISO 8601 standard, read the article on Wikipedia. For the purposes of this post there are just three points you need to know about this standard:

• It always expresses dates and times from the largest term to the smallest, i.e. YYYY-MM-DD.
• It counts Monday as the first day of the week, not Sunday.
• It counts the first week of the year as the week containing the first Thursday of the year, not the week containing the first day of the year.

Each of these facets of the ISO 8601 standard are at odds with the default ways in which T-SQL handles dates.  There are workarounds to each one, though each workaround is more complex than the last. I'll start with the easiest first.

Express Dates and Times from the Largest Term to the Smallest

The default ways to get a datetime value and express it as a string in date notation are the following:

convert(varchar, getdate())
cast(getdate() as varchar)

Both of these will return the result in the same format. For July 7th, 2011 at 4:13 pm, it would look like this:

Jul 7 2011  4:13PM

Apart from the three-letter abbreviation for the month and lack of a comma, this is a fairly typical way of expressing the date and time in America. But it is not at all in keeping with the ISO standard. Fixing this is fairly easy, though, because the CONVERT() function has an optional format parameter, and there are values that will return true ISO-formatted date and time results. Here are the values and their outputs for the same day and time as above:

convert(varchar, getdate(), 112) = 20110707 (date only)
convert(varchar, getdate(), 108) = 16:13:24 (time only)
convert(varchar, getdate(), 126) = 2011-07-07T16:13:24.173 (complete date and time)

For the last variation, notice the T separator between date and time. Also notice the inclusion of milliseconds as a decimal fraction of a second. The last format also includes hyphens in the date where the date-only format did not. Both variations are acceptable in the ISO 8601 standard. The format without the hyphens is the "basic format," and the format with the hyphens is the "extended format."

Count Monday as the First Day of the Week

This is actually the key reason why churches may be interested in using an ISO week even if they live in the United States or other countries that do not use the ISO 8601 standard as a general rule. Most churches that have Friday or Saturday worship events want to count the following Sunday worship as part of the same weekend for statistical purposes. The ISO standard does that be lumping Sunday in with the prior six days.

However, this is uniquely tricky for the ShelbyQUERY environment because it does not allow the command SET DATEFIRST 1, which would automatically tell SQL Server to count Monday as the first day of the week. One simple workaround is to simply subtract one day from the date when doing comparisons based on which week the date belongs to. This will treat Sunday as if it were Saturday of the prior week, and it will treat Monday as if it were the first day of the week. Simply using getdate()-1 wherever you use getdate() will do that trick. Just remember not to subtract the day when you want to display the actual calendar date.

For statistical calculations based on a Monday through Sunday week, group the values by the ISO week and the ISO "week year" (i.e., the year in which the week falls -- which can be a different year than the calendar year because the first few days and last few days of the year can fall into the other year's week count). How to calculate the ISO week value is the next topic.

Count the first week of the year as the week containing the first Thursday of the year, not the week containing the first day of the year.

This is the most difficult part of ISO, and it comes down to calculating the week of the year. The DATEPART() function has a week parameter option that returns the week of the year; however, it does not follow ISO rules. It will count January 1st as being in the first week of the year no matter when it falls during the week. If you are using SQL Server 2008 or later you have it easy because Microsoft introduced a new DATEPART() parameter option in 2008 that does follow the ISO 8601 standard: iso_week. If you are using SQL Server 2005 or earlier, though, you are going to have to calculate it the hard way.

This is the algorithm I use  in the query below to calculate the ISO week of the year:

1. Let TargetDate equal the date for which we want to know the ISO week value.
2. Let CurrentThursday equal the date of the Thursday associated with the same week as the TargetDate (taking into account that Sunday belongs with the prior Thursday).
3. Let FirstThursday equal the date of the Thursday of the week containing January 4th (by definition January 4th is always in the first ISO week of the year), basing that on the year value of the CurrentThursday (not the TargetDate).
4. Let ISO_Week_Value equal the difference, in weeks, between the FirstThursday and the CurrentThursday, plus one.

Here is a query that uses variables to reflect each step of the algorithm and includes two AllInOne versions that rely on only the @TargetDate variable and no others. The FROM clause at the end is only necessary in ShelbyQUERY because of a requirement in that environment to always include a FROM clause.


declare @DateOffset as smallint, @ThursdayOffset as smallint, @TargetDate as datetime, @CurrentThursday as datetime, @FirstThursday as datetime, @ISO_WeekNumber as tinyint

/* The @DateOffset is used to make sure that Monday - Wednesday are always in the same week as the following Thursday and that Friday - Sunday are always in the same week as the prior Thursday no matter what the @@datefirst value is.
The @ThursdayOffset is used to find Thursday no matter what the @@datefirst value is. */ 

set @DateOffset = case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end
set @ThursdayOffset = case when @@datefirst < 5 then 5 - @@datefirst else 12 - @@datefirst end

set @TargetDate = getdate()


set @CurrentThursday = dateadd(day, @ThursdayOffset - datepart(dw, @TargetDate + @DateOffset), @TargetDate + @DateOffset)

set @FirstThursday = dateadd(day, @ThursdayOffset - datepart(dw, cast('1/4/' + datename(year, @CurrentThursday) as datetime) + @DateOffset), cast('1/4/' + datename(year, @CurrentThursday) as datetime) + @DateOffset)

set @ISO_WeekNumber = datediff(week, @FirstThursday, @CurrentThursday) + 1

select
 TestDate = @TargetDate,
 CurrentThursday = @CurrentThursday,
 FirstThursday = @FirstThursday,
 ISO_WeekNumber = @ISO_WeekNumber,
 ISO_WeekYear = year(@CurrentThursday),

 ISO_WeekNumber_AllInOne = datediff(week, dateadd(day, case when @@datefirst < 5 then 5 - @@datefirst else 12 - @@datefirst end - datepart(dw, cast('1/4/' + datename(year, dateadd(day, case when @@datefirst < 5 then 5 - @@datefirst else 12 - @@datefirst end - datepart(dw, @TargetDate + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end), @TargetDate + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end)) as datetime) + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end), cast('1/4/' + datename(year, dateadd(day, case when @@datefirst < 5 then 5 - @@datefirst else 12 - @@datefirst end - datepart(dw, @TargetDate + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end), @TargetDate + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end)) as datetime) + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end), dateadd(day, case when @@datefirst < 5 then 5 - @@datefirst else 12 - @@datefirst end - datepart(dw, @TargetDate + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end), @TargetDate + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end)) + 1,
  ISO_WeekYear_AllInOne = year(dateadd(day, case when @@datefirst < 5 then 5 - @@datefirst else 12 - @@datefirst end - datepart(dw, @TargetDate + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end), @TargetDate + case when @@datefirst > 4 then @@datefirst - 8 when @@datefirst > 1 then @@datefirst - 1 else 0 end))
 
from (select A = count(*) from Shelby.NANames) a

 

Find the First Non-Null Value in a List

Recently a customer asked how to list the first available phone number for an individual, regardless of what phone type it might be. If there was a Main/Home phone, use it. But if not, list the cell phone instead. If the person had neither but did have a work phone, that would do fine. They only wanted one phone number column in the results, though.

In more technical terms, the customer wanted the first non-null phone number value from the NANames table for a given NameCounter, given the priority of Main/Home first if available, then cell, then work. As it happens, T-SQL provides a very handy function that returns the first non-null value from a list. That function is COALESCE. It works exactly like ISNULL, but instead of taking only two values in the parameter list, COALESCE can take any number of values. The first non-null value in the list is returned as the value of the function. If all the values are null, the value of the function is null.

Here is a simple query on the ShelbyDB database to show how COALESCE can return the first non-null phone number value from a list of phone type values:

select
 Name = FirstMiddle + ' ' + LastName,
 PhoneNumber = coalesce('Home: ' + MainPhones.PhoneNu, 'Cell: ' + CellPhones.PhoneNu, 'Work: ' + WorkPhones.PhoneNu)
from
 Shelby.NANames as Names left join
 Shelby.NAPhones as MainPhones on Names.NameCounter = MainPhones.NameCounter and MainPhones.PhoneCounter = 1 left join
 Shelby.NAPhones as CellPhones on Names.NameCounter = CellPhones.NameCounter and CellPhones.PhoneCounter = 4 left join
 Shelby.NAPhones as WorkPhones on Names.NameCounter = WorkPhones.NameCounter and WorkPhones.PhoneCounter = 2

This query assumes that the Main/Home PhoneCounter value is 1 (it always it), that the Work PhoneCounter is 2 (it always is) and that the Cell Phone PhoneCounter is 4 (it often is, but not always). You should verify the PhoneCounter values for the phone types you want if you use this type of query approach in your own Shelby v.5 database.

In the example I also appended a descriptor to identify which type of phone number was listed. Remember that concatenating a literal string to a null value still results in a null value.

COALESCE comes in handy for any situation where you want to supply the "first available" value from a list of possible values. I have used it to supply either Greeting Type, Salutation, or First Middle name, whichever is available. I have used it to populate an address column with either a preferred address type or the Main/Home address if the preferred type is not available.