Sort list by order number with record grouping - tsql

Question

I have a list of orders. I would like to sort the list in the way that if there are more than one order placed by the same customer, the orders are grouped. It is hard to explain by words so here is an example:
This is the list sorted by Order No:
<table>
<tr>
<th>Customer</th>
<th>Order No</th>
</tr>
<tr>
<td>A</td>
<td>1</td>
</tr>
<tr>
<td>B</td>
<td>2</td>
</tr>
<tr>
<td>C</td>
<td>3</td>
</tr>
<tr>
<td>A</td>
<td>4</td>
</tr>
<tr>
<td>A</td>
<td>5</td>
</tr>
<tr>
<td>D</td>
<td>6</td>
</tr><tr>
<td>C</td>
<td>7</td>
</tr>
</table>
I would like this list to look like this:
<table>
<tr>
<th>Customer</th>
<th>Order No</th>
</tr>
<tr>
<td>A</td>
<td>1</td>
</tr>
<tr>
<td>A</td>
<td>4</td>
</tr>
<tr>
<td>A</td>
<td>5</td>
</tr>
<tr>
<td>B</td>
<td>2</td>
</tr>
<tr>
<td>C</td>
<td>3</td>
</tr>
<tr>
<td>C</td>
<td>7</td>
</tr>
<tr>
<td>D</td>
<td>6</td>
</tr>
</table>
I will be very grateful for any hint :)
Thank you!

Answer 1

You can create a map of customers and orders.
For each map entry create a list of ordernumbers.
Doing so you can sort every order list.
Example:
const list = [
{ customer: 'A', ordernumber: 2 },
{ customer: 'B', ordernumber: 1},
{ customer: 'A', ordernumber: 1 },
{ customer: 'A', ordernumber: 3 }
]
customerOrderMap = {}
list.forEach(element => customerOrderMap[element.customer] = [])
list.forEach(element => customerOrderMap[element.customer].push(element.ordernumber))
Object.keys(customerOrderMap).forEach(key => {
console.log(customerOrderMap[key].sort((a, b) => a - b))
})
console.log(customerOrderMap)