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We have made a couple of enhancements to the aggregate query feature of Fetch XML. These updates have shipped for version 4.0 as part of UR2 and for version 3.0 as documented in KB Article 960079. So far we only supported the count aggregate function which essentially did a count(*) on the base table of the entity.
We have enhanced this functionality to add a new aggregate operation countcolumn which now performs the SQL count operation for a given column. It also support the distinct keyword which only counts unique columns. If the distinct keyword is not specified with a countcolumn aggregate, its value defaults to false.
Here is a table that summarizes the Fetch aggregate types and its equivalent SQL translation:
CRM Fetch XML
<attribute name='address1_city' aggregate='count' alias='citycount' />
SELECT COUNT(*) AS 'citycount' FROM Account
<attribute name='address1_city' aggregate='countcolumn' alias='citycount' />
SELECT COUNT(address1_city) AS 'citycount' FROM Account
<attribute name='address1_city' aggregate='countcolumn' alias='citycount' distinct='true' />
SELECT COUNT(DISTINCT address1_city) AS 'citycount' FROM Account
Key: Existing Feature, New Feature
Here are a couple of examples for using these features:
Query to return a count of all Accounts which have a county specified in their address.
1: Query to return a count of all Accounts which have a county specified in their address.
2: <fetch aggregate='true'>
3: <entity name='account'>
4: <attribute name='address1_county' aggregate='countcolumn' alias='countyAccounts' />
Query to return a count of states in which we have an account. This uses the distinct keyword which counts a state only once.
1: <fetch aggregate='true'>
2: <entity name='account'>
3: <attribute name='address1_stateorprovince' aggregate='countcolumn' alias='countStates' distinct='true' />
Nice enhancement. However, why does FetchXML not support average, sum or stdev? The FetchXML xsd in the CRM 4.0 SDK states that it does:
<xs:enumeration value="count" />
<xs:enumeration value="average" />
<xs:enumeration value="sum" />
<xs:enumeration value="stdev" />
But, it does not. Are you planning to support the other aggregations too, or will you update the SDK to reflect the true capabilities of the FetchXML functionality?
The XSD is a bit out of sync with what was implemented unfortunately in CRM 4.0. However, in CRM 5, expect to see support for the following features:
1) Aggregate support for MIN, MAX, AVG, SUM, COUNT, COUNTCOLUMN
2) Group By Support in Fetch and Special Grouping Support for DateTime Fields based on Day, Month, Week and Year.
Aggregating, true, but no group by. These SQL queries return single rows -- these are not sets of city counts.
Yes, I would improve these examples by changing the aliases, respectively, to 'k', 'citiedcount' and 'citycount'.
Any chance you could support Min and Max on date fields please?