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This gives you average of reading for each serial number:<br />

<pre><code id="code-20-38299303-1">SELECT [Serial Number]
	 , avg(Reading)
FROM YourTable
GROUP BY [Serial Number]</code></pre>
<br />
this query gives you max difference of the smalles reading and biggest reading for each serial number:<br />
<br />

<pre><code id="code-20-38299303-2">SELECT [Serial Number]
	 , Max(Reading) - Min(Reading)
FROM YourTable
GROUP BY [Serial Number]</code></pre>
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This gives you average of reading for each serial number:


SELECT [Serial Number]
	 , avg(Reading)
FROM YourTable
GROUP BY [Serial Number]


this query gives you max difference of the smalles reading and biggest reading for each serial number:



SELECT [Serial Number]
	 , Max(Reading) - Min(Reading)
FROM YourTable
GROUP BY [Serial Number]

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<div class="content wysiwyg-content">
I have data in a table like this<br />
<br />
Date &nbsp;| &nbsp; Serial Number &nbsp;| &nbsp; Reading<br />
5-1-2012| 12345|12345<br />
5-2-2012|12345|12348<br />
<br />
<br />
So i figured out how to get the diference between the 2 values as &nbsp;3 for 5-2.<br />
<br />
&nbsp; and i can run this now for all on one serial number but now i want average how much it changes with all 250 items. &nbsp;So i have 250 unique seril nubers. &nbsp;and the readings are all different numbers, &nbsp;but the differences are relatively close. &nbsp;I want to average the change between values. &nbsp;ANy one know how to do this?
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I have data in a table like this

Date  |   Serial Number  |   Reading
5-1-2012| 12345|12345
5-2-2012|12345|12348


So i figured out how to get the diference between the 2 values as  3 for 5-2.

  and i can run this now for all on one serial number but now i want average how much it changes with all 250 items.  So i have 250 unique seril nubers.  and the readings are all different numbers,  but the differences are relatively close.  I want to average the change between values.  ANy one know how to do this?

Average query based on difference

Microsoft SQL Server is a suite of relational database management system (RDBMS) products providing multi-user database access functionality.SQL Server is available in multiple versions, typically identified by release year, and versions are subdivided into editions to distinguish between product functionality. Component services include integration (SSIS), reporting (SSRS), analysis (SSAS), data quality, master data, T-SQL and performance tuning.