Hi Saie,

Can you try checking the below lightning component implementation:

<aura:component controller=”PaginationController”>
<aura:attribute name=”accounts” type=”account[]” />
<aura:attribute name=”contacts” type=”contact[]” />

<aura:handler name=”init” value=”{!this}” action=”{!c.doInit}”/>

<br />
<table class=”slds-table slds-table_bordered slds-table_cell-buffer”>
<thead>
<tr class=”slds-text-title_caps”>
<th scope=”col”>

Contact Id
</th>
<th scope=”col”>

Contact Name
</th>
</tr>
</thead>
<tbody>
<aura:iteration items=”{!v.contacts}” var=”contact”>
<tr>
<th scope=”row” data-label=”Contact Id”>

{!contact.Id}
</th>
<td data-label=”Contact Name”>

{!contact.Name}
</td>
</tr>
</aura:iteration>
</tbody>
</table>
</aura:component>

===================================== testCmpController.js ====================================

({
doInit : function(component, event, helper) {
helper.loadAccounts(component);
},

onSelectChange : function(component, event, helper) {
var selected = component.find(“dd1”).get(“v.value”);
//alert(‘selected: ‘ + component.get(‘v.accounts’)[0].Contacts[0].Name);
var abc = component.get(‘v.accounts’);

for(i=0; i<abc.length;i++)
{
if(abc[i].Id == selected)
{
component.set(“v.contacts”, abc[i].Contacts);
//alert(abc[i].Contacts);
}
}

//do something else
}

})

===================================== testCmpHelper.js ====================================================
({
loadAccounts : function(cmp) {
var action = cmp.get(“c.getAccounts”);
action.setCallback(this, function(response) {
var state = response.getState();
if (state === “SUCCESS”) {
cmp.set(“v.accounts”, response.getReturnValue());
}
});
$A.enqueueAction(action);
}
})

====================================== PaginationController.apxc ===========================================
public class PaginationController {

@AuraEnabled
public static List<Account> getAccounts(){
return [select Id, Name, (Select Id, name from contacts) from account where Id IN (‘0012800000Y0H09AAF’, ‘0012800000Y0H0FAAV’, ‘0012800000hBU2qAAG’, ‘0012800000smvlCAAQ’)];
}

}

Reference: https://umangsinghal.wordpress.com/2017/05/23/change-table-value-on-the-basis-of-drop-down-in-lightning/

Let me know if it helps you and close your query by marking it as solved so that it can help others in the future.  

Thanks.