title: Flutter DataTable - how to make a table with varying number of datacell (make some datacell span multiple columns)
body: <p>I intend to output a table with 2 rows, the first row contains 3 columns, the second one contains just one, meaning the cell in the second row should span 3 columns.</p>
  <p>Here's my code:</p>
  <pre><code> DataTable(
        columns: [
          DataColumn(label: Text('#')),
          DataColumn(label: Text('Name')),
          DataColumn(label: Text('Price')),
        ],
        rows: [
          DataRow(cells: [
            DataCell(Text('1')),
            DataCell(Text(orderItem.title)),
            DataCell(Text(orderItem.price.toString())),
          ]),
          DataRow(cells: [
            DataCell('Total: ${orderItem.price}'),
          ]),
        ],
  )
  </code></pre>
  <p>Since the second row has only 1 datacell, this is the error that I'm getting:</p>
  <pre><code>'package:flutter/src/material/data_table.dart': Failed assertion: line 480 pos 15: '!rows.any((DataRow row) =&gt; row.cells.length != columns.length)': is not true.
  </code></pre>
  <p>How do I make the second row cell span 3 columns?</p>