Merge pull request MicrosoftDocs#3126 from MicrosoftDocs/pehecke-fetchxml-changes

Column comparision in queries

Author: phecke

powerapps-docs/developer/common-data-service/TOC.yml

@@ -27,6 +27,8 @@
       href: use-fetchxml-left-outer-join-query-records-not-in.md
     - name: Page large result sets with FetchXML
       href: org-service/page-large-result-sets-with-fetchxml.md
+    - name: Use column comparison in queries
+      href: column-comparison.md
   - name: "Use SQL to query data (Preview)"
     href: cds-sql-query.md
   - name: Saved Queries

powerapps-docs/developer/common-data-service/column-comparison.md

@@ -0,0 +1,69 @@
+---
+title: "Use column comparison in queries (Common Data Service) | Microsoft Docs" # Intent and product brand in a unique string of 43-59 chars including spaces
+description: "Learn how to compare columns when querying business data." # 115-145 characters including spaces. This abstract displays in the search result.
+ms.custom: ""
+ms.date: 07/08/2020
+ms.reviewer: "pehecke"
+ms.service: powerapps
+ms.topic: "article"
+author: "NHelgren" # GitHub ID
+ms.author: "nhelgren" # MSFT alias of Microsoft employees only
+manager: "mayadu" # MSFT alias of manager or PM counterpart
+search.audienceType: 
+  - developer
+search.app: 
+  - PowerApps
+  - D365CE
+---
+
+# Use column comparison in queries
+
+In the Common Data Service, users can perform a column comparison for the
+following condition operators using FetchXML, Web API, or the SDK API:
+
+- Equal
+- NotEqual
+- GreaterThan
+- GreaterEqual
+- LessThan
+- LessEqual
+
+This will allow the comparison of an attribute against a specific value and
+return all found records, or allow the comparison of two attributes to return
+all records with a matching value.
+
+## Limitations
+
+Listed below are the limitations for the current Common Data Service column comparison support.
+
+- Only two columns may be compared at a time.
+- Multi-value condition operators are not supported (i.e., "in").
+- Extended condition operators are not supported (i.e., "creditlimit \> spends+1000").
+- Incompatible attribute comparison is not supported. For example, "int vs. int" attributes is a valid comparison but "int vs. string" attributes is not valid comparison.
+
+## Column comparison using FetchXML
+
+The following example shows how to compare columns using FetchXML:
+
+```xml
+<fetch>
+  <entity name='contact' >
+    <attribute name='firstname' />
+    <filter>
+      <condition attribute='firstname' operator='eq' valueof='lastname'/>
+    </filter>
+  </entity>
+</fetch>
+```
+
+For FetchXML requests, a new node `valueof` has been added inside the condition
+node. The `valueof` tag is used to identify the attribute that is being compared
+to the selected attribute. In the above example, the 'firstname' column is being
+compared against the 'lastname' column and will return any records that contain
+the same value across both attributes.
+
+### See Also
+
+[Use FetchXML to construct a query](use-fetchxml-construct-query.md)  
+[Column comparison using the Web API](webapi/query-data-web-api.md#column-comparison-using-the-web-api)  
+[Column comparison using the SDK API](org-service/use-conditionexpression-class.md#column-comparison-using-the-sdk-api)

powerapps-docs/developer/common-data-service/org-service/use-conditionexpression-class.md

@@ -82,7 +82,41 @@ condition3.Operator = ConditionOperator.Equal;
 condition3.Values.Add(AccountState.Active);  
 
 ```  
-  
+
+## Column comparison using the SDK API
+
+The following example shows how to compare columns using SDK API and the Organization service:
+
+```csharp
+public ConditionExpression
+(
+  string attributeName,
+  ConditionOperator conditionOperator,
+  bool compareColumns,
+  object value
+)
+
+public ConditionExpression
+(
+  string attributeName,
+  ConditionOperator conditionOperator,
+  bool compareColumns,
+  object[] values
+)
+```
+
+In the SDK, two APIs are introduced to support column comparison. The
+first identifies the original attribute, the second allows
+for the inclusion of the attribute you want to compare it against.
+
+If `compareColumns` is passed in as `true`, it will compare the two attributes
+and return all records that match.
+
+If a `false` value is passed, it will return all records for one attribute and
+return values that match the provided value.
+
+More information: [Use column comparison in queries](../column-comparison.md)
+
 ### See also  
  [Building Queries](build-queries-with-queryexpression.md)   
  [Build Queries with QueryExpression](build-queries-with-queryexpression.md)   

powerapps-docs/developer/common-data-service/webapi/query-data-web-api.md

@@ -861,6 +861,16 @@ The change tracking feature allows you to keep the data synchronized in an effic
 
 More information: [Use change tracking to synchronize data with external systems](../use-change-tracking-synchronize-data-external-systems.md).
 
+## Column comparison using the Web API
+
+The following example shows how to compare columns using the Web API:
+
+```http
+https://<environment-root>/contacts?$select=firstname&$filter=firstname eq lastname
+```
+
+More information: [Use column comparison in queries](../column-comparison.md)
+
 ### See also
 
 [Web API Query Data Sample (C#)](samples/query-data-csharp.md)<br />