Retrieve Many-to-Many (N:N) Relationship Records using Web API in Dynamics 365 using JavaScript

The below code can be used when you want to read N:N or many-to-many related records and do some logics for validations. As N:N intersect table cannot be found in Advance Find you can check the name of intersect table from powerapps solution.

The below code runs on a command button click and checks if a related records of the current records having some field value and alerting accordingly.

function VarifyStudentReward(executionContext)
{
	var recordId = executionContext.data.entity.getId();
	var fetchXmlQuery = "<fetch version='1.0' output-format='xml-platform' mapping='logical' distinct='true'>"+
			"<entity name='soft_reward'>"+
			"<attribute name='soft_name' />"+
			"<attribute name='soft_category' />"+
			"<order attribute='soft_name' descending='false' />"+
				"<link-entity name='soft_reward_soft_student' from='soft_rewardid' to='soft_rewardid' visible='false' intersect='true'>"+
					"<link-entity name='soft_student' from='soft_studentid' to='soft_studentid' alias='ab'>"+
					"<attribute name='soft_name' />"+
					"<attribute name='soft_phonenumber' />"+
						"<filter type='and'>"+
							"<condition attribute='soft_studentid' operator='eq' value='"+recordId+"' />"+
						"</filter>"+
					"</link-entity>"+
				"</link-entity>"+
			"<filter type='and'>"+
				"<condition attribute='soft_category' operator='in'>"+
					"<value>408260001</value>"+
					"<value>408260000</value>"+
				  "</condition>"+
			"</filter>"+
			"</entity>"+
			"</fetch>";
		
		var globalContext = Xrm.Utility.getGlobalContext();
		var req = new XMLHttpRequest();
		req.open(
		  "GET",
		  globalContext.getClientUrl() +
			"/api/data/v9.2/soft_rewards?fetchXml=" +
			encodeURIComponent(fetchXmlQuery),
		  true
		);
		req.setRequestHeader("Prefer", 'odata.include-annotations="*"');
		req.onreadystatechange = function() {
		  if (this.readyState === 4) {
			req.onreadystatechange = null;
			if (this.status === 200) {
			  var results = JSON.parse(this.response);
			  if(results.value.length >= 1)
				alert("You are a top student");
			  else
				alert("You are not a top student");  
			} else {
			  alert(this.statusText);
			}
		  }
		};
		req.send();
}

hope this helps.

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