Update overview-of-search.md

Redux of _include, _revinclude content for FHIR update (trigger on Ketki).

Author: KendalBond007

articles/healthcare-apis/fhir/overview-of-search.md

@@ -129,8 +129,8 @@ FHIR specifies a set of search result parameters to help manage the information
 | -------------------------  | -------------------- | ------------------------- | ------------|
 | `_elements`                     | Yes                  | Yes                       | |
 | `_count`                        | Yes                  | Yes                       | `_count` is limited to 1000 resources. If it's set higher than 1000, only 1000 are returned and a warning will be included in the bundle.                               |
-| `_include`                      | Yes                  | Yes                       | Items retrieved with `_include` are limited to 100. `_include` on PaaS and OSS on Azure Cosmos DB doesn't support `:iterate` [(#2137)](https://github.com/microsoft/fhir-server/issues/2137).                               |
-| `_revinclude`                   | Yes                  | Yes                       |Items retrieved with `_revinclude` are limited to 100. `_revinclude` on PaaS and OSS on Azure Cosmos DB doesn't support `:iterate` [(#2137)](https://github.com/microsoft/fhir-server/issues/2137). There's also an incorrect status code for a bad request: [#1319](https://github.com/microsoft/fhir-server/issues/1319).                            |
+| `_include`                      | Yes                  | Yes                       | `_include` on PaaS and OSS on Azure Cosmos DB doesn't support `:iterate` [(#2137)](https://github.com/microsoft/fhir-server/issues/2137).                               |
+| `_revinclude`                   | Yes                  | Yes                       | `_revinclude` on PaaS and OSS on Azure Cosmos DB doesn't support `:iterate` [(#2137)](https://github.com/microsoft/fhir-server/issues/2137). There's also an incorrect status code for a bad request: [#1319](https://github.com/microsoft/fhir-server/issues/1319).                            |
 | `_summary`                      | Yes             | Yes                   | |
 | `_total`                        | Partial              | Partial                   | `_total=none` and `_total=accurate`                               |
 | `_sort`                         | Partial              | Partial                   | `sort=_lastUpdated` is supported on the FHIR service. For the FHIR service and the OSS SQL DB FHIR servers, sorting by strings and dateTime fields are supported. For Azure API for FHIR and OSS Azure Cosmos DB databases created after April 20, 2021, sort is supported on first name, last name, birthdate, and clinical date.             |
@@ -144,6 +144,80 @@ Note:
 
 By default, the FHIR service in Azure Health Data Services is set to lenient handling. This means that the server ignores any unknown or unsupported parameters. If you want to use strict handling, you can include the `Prefer` header and set `handling=strict`.
 
+#### _include and _revinclude searches
+
+The FHIR service support search queries using the `_include` and `_revinclude` parameters. These parameters allow for the retrieval of reference resources in the search results.  
+
+The `_include` search parameter enables the retrieval of a particular FHIR resource, as well as any other FHIR resources that are referenced by it. When used in a query, the `_include` parameter returns the specified resource *and* its referenced resources. The `_revinclude` search parameter operates in the reverse, allowing the retrieval of a resource along with any other resources that reference it, providing a way to search for resources based on their relationships with other resources. For detailed information on include and revinclude in search parameters, refer to the [FHIR Search Documentation](https://www.hl7.org/fhir/R4/search.html#revinclude).
+
+#### Request parameters
+
+When executing a search request with `_include` and `_revinclude` parameters, the following optional parameters can be used to control the count.
+
+| **Name** | **Value** | **Description** |
+| -------------------------  | -------------------- | ------------------------- |
+| `_count` | Default value: 10 Max value: 1000 | The value represents the number of targeted resources to be retrieved per request. The value can be set up to 1000. When the parameter is not provided, it is set to 10. |
+| `_includesCount` | Default value: 1000 | The value represents the number of matches resources referenced by target resources to be retrieved per request. |
+
+A maximum of 1000 items are included in the response from `_include` and `_revinclude` searches. If there are more than 1,000 matched items, a link is provided allowing you to navigate the complete result set. 
+
+In the following example, a search request for Observations is made for Patient with Identifier 123.
+
+```
+GET {{FHIR_URL}}/Observation?subject.identifier=123&_include=Observation:subject&_includesCount=10
+```
+
+The response will have Observation data for Patient 123. The matched resources are provided 10 per page, with a link provided to navigate the complete result set.
+
+```
+          { 
+
+  	"resourceType": "Bundle", 
+
+ 	 "id": "b5491e39-8f8f-4405-a4cf-2a6716755d73", 
+
+  	"meta": { 
+
+    	"lastUpdated": "2025-04-10T21:09:42.6517693+00:00" 
+
+  	}, 
+
+  	"type": "searchset", 
+
+  "	link": [ 
+
+    	{ 
+
+      	"relation": "next", 
+
+      	"url": "{{FHIR_URL}}/Observation?subject.identifier=123&_include=Observation:subject&_includesCount=10&ct=er97f5lRTbShgbGOqaGhgbGlsZGFmaWJiYWBgYGpSSwAAAD%2F%2Fw%3D%3D" 
+
+    	}, 
+
+   	 { 
+
+    	  "relation": "related", 
+
+      	"url": "{{FHIR_URL}}/Observation/$include?subject.identifier=123&_include=Observation:subject&_includesCount=10&includesCt=er97f5lRTbShgbGOqaGhgbGlsZGFmaWJiYWBgYGhAaaYqYmOqQUWYaNYAAAAAP%2F%2F" 
+
+   	 }, 
+
+    	{ 
+
+    	  "relation": "self", 
+
+     	 "url": "{{FHIR_URL}}/Observation?subject.identifier=123&_include=Observation:subject&_includesCount=10” 
+
+    	} 
+
+  	], 
+
+  "entry": [….] 
+
+}
+```
+
+
  ## Chained & reverse chained searching
 
 A [chained search](https://www.hl7.org/fhir/search.html#chaining) allows you to perform fine-targeted queries for resources that have a reference to another resource. For example, if you want to find encounters where the patient’s name is Jane, use: