Untitled

 <DataTable :value="mainData" :expandedRows="expandedRows" @update:expandedRows="updateExpandedRows" dataKey="id">
      <!-- Define Columns for Main DataTable -->
      <Column field="name" header="Name"></Column>
      <Column field="age" header="Age"></Column>
      <Column field="email" header="Email"></Column>
      
      <!-- Expandable Row Template -->
      <template #expandedRow="{ data }">
        <DataTable :value="data.subData" dataKey="id" class="p-datatable-sm">
          <!-- Define Columns for Sub DataTable -->
          <Column field="itemName" header="Item Name"></Column>
          <Column field="itemValue" header="Item Value"></Column>
        </DataTable>
      </template>
    </DataTable>