All posts by Jon Culp

Collapse and Concatenate Rows

I had a need to concatenate  and comma separate some multi-row data into an array of values with each having an unknown number of elements, in other words, take a many to one parent-child relationship and collapse the many child rows into the one parent record and separate the child record values with a comma.  In the past, my default method to solve this problem was to build a temporary  table  and then use a loop to iterate through a data set and append the elements by updating rows in the temporary table, or use a common table expression with anchor and recursive members.  Recently I stumbled upon the “stuff” and “for xml” functions.  I had seen these functions  before but never took the time to understand their potential use.  These function can be used to solve the problem mentioned.

T-SQL For XML (Path Mode)

Function Description: A SELECT query returns results as a rowset. You can optionally retrieve formal results of a SQL query as XML by specifying the FOR XML clause in the query. The FOR XML clause can be used in top-level queries and in sub queries. The top-level FOR XML clause can be used only in the SELECT statement. In sub queries, FOR XML can be used in the INSERT, UPDATE, and DELETE statements. It can also be used in assignment statements.

In a FOR XML clause, you specify one of these modes: RAW, AUTO, EXPLICIT, PATH.  We will only use PATH for this exercise.

The PATH mode together with the nested FOR XML query capability provides the flexibility of the EXPLICIT mode in a simpler manner.

The EXPLICIT mode allows more control over the shape of the XML. You can mix attributes and elements at will in deciding the shape of the XML. It requires a specific format for the resulting rowset that is generated because of query execution. This rowset format is then mapped into XML shape. The power of EXPLICIT mode is to mix attributes and elements at will, create wrappers and nested complex properties, create space-separated values (for example, OrderID attribute may have a list of order ID values), and mixed contents.

I will not list the syntax for this function because it can get pretty complex very quickly for all of the options.  Instead, you can see in the example I just use it to concatenate the rows into a comma separated array.   Any other XML is basically ignored by passing  in the argument “Path (”)”.

(More information on For XML)

T-SQL Stuff Function

Function Description: The STUFF function inserts a string into another string. It deletes a specified length of characters in the first string at the start position and then inserts the second string into the first string at the start position.

Function Syntax: STUFF ( character_expression , start , length ,character_expression )

(More Information on the Stuff function)

Example Problem

List database users and include all roles of which a user is a member, separated by comma.

Solution using Stuff and For XML

  • “For XML” is used to collapse and concatenate the row data into a single array.
  • “Stuff” is used to remove the leading comma.
  • Note that we are using a correlated subquery when we reference “dp.principal_id” in order to limit our roles and role members to our database principals in the main outer query.

Output:

principal_id type_desc create_date modify_date Roles
5 SQL_USER 11/13/2002 6/19/2010 db_owner
7 SQL_USER 11/13/2002 6/19/2010 db_owner,db_datareader,db_datawriter
8 WINDOWS_USER 3/26/2009 3/26/2009 db_datareader
10 WINDOWS_USER 3/16/2008 3/16/2008 db_datareader
11 SQL_USER 7/11/2008 6/19/2010 WebViews
13 SQL_USER 7/25/2014 7/25/2014 role_proxyusers
14 WINDOWS_USER 3/12/2009 3/12/2009 db_datareader
16 SQL_USER 7/25/2014 7/25/2014 role_proxyusers
18 SQL_USER 8/26/2005 6/19/2010 db_owner
19 WINDOWS_USER 6/2/2009 6/2/2009 MSReplPAL_9_1,db_datareader
20 WINDOWS_GROUP 10/3/2005 10/3/2005 db_datareader
21 SQL_USER 7/14/2009 5/2/2016 role_proxyusers,db_datareader,db_denydatawriter

Microsoft SQL Server Developer Edition is now free

https://blogs.technet.microsoft.com/dataplatforminsider/2016/03/31/microsoft-sql-server-developer-edition-is-now-free/

“Exciting news! Starting today, SQL Server 2014 Developer Edition is now a free download for Visual Studio Dev Essentials members (you will be prompted to sign in to Visual Studio Dev Essentials before you can download SQL Server 2014 Developer Edition). We are making this change so that all developers can leverage the capabilities that SQL Server 2014 has to offer for their data solution, and this is another step in making SQL Server more accessible. SQL Server Developer Edition is for development and testing only, and not for production environments or for use with production data.”

“SQL Server 2016 Developer Edition, when released later this year, will also be free. To learn more about the exciting new features in SQL Server 2016, read the datasheet.”

Create Read Only User in Azure DB

I have been struggling with creating a user who has read only access to an azure database and finally figured it out.  The key is connecting to the right database in a new session when executing the t-sql commands.  This is because you can not execute a “use” statement, change the database in the current session via the GUI, and you can not make named references to databases in your t-sql.

server_name.database_name.schema_name.object_name

Validate user has read only permissions by connecting to database using these new credentials and executing something like “CREATE TABLE dbo.test (test datetime);”, which should return an error message indicating permission denied.

More information on managing database access and login security in azure: https://azure.microsoft.com/en-us/documentation/articles/sql-database-manage-logins/

WiFi Range Heat Mapping

I wanted to compare WiFi coverage of two different wireless access points and their various configurations in my house, and also check for dead spots.  One quick and cheap way to do this that I have come across is using a free product called Ekahau HeatMapper.

Ekahau HeatMapper allows you to walk around your home or office and capture information about WiFi signals in various spots, and then the software aggregates this information into a banded topographical map.

Continue reading WiFi Range Heat Mapping

Publish Google Analytics Reports to the Web using Power BI

There is a feature in Power BI which allows you to connect to your google analytics data, and there is a new preview feature which allows publishing content to the web in an iframe.  In this post I have combined both features together to display my website statistics to the web.

  1. Connect to Google Analytics: https://powerbi.microsoft.com/en-us/documentation/powerbi-content-pack-google-analytics/
  2. Publish to Web: https://powerbi.microsoft.com/en-us/blog/announcing-power-bi-publish-to-web/
Here is the result:
(View Larger)


Note: PowerBI has trouble rendering in Chrome in some cases.  If you are using Chrome and can not see the dashboard then try another browser.  Hopefully Microsoft will resolve this problem.

Video: Business Intelligence with Power BI

I’ve been catching myself up on what Microsoft is doing lately regarding Business Intelligence.  After spending days reading Microsoft documentation and testing some various configurations of Power BI, Gateway,Azure, and SSRS, I came across this video that goes over some history and then gets right into Power BI and some competing tools.  I suspect Microsoft is working toward merging Power BI and SSRS based on some of their SQL Server public previews.