Custom row number in SQL - sql

Question

I am using a software which doesn't have a feature on custom row number. In order to resolve my issue, I have to tweak it on my SQL and create a custom column for the custom row number. Here is what I want to do as my custom row number along with my select statement:
li{
list-style-type: none;
}
<ul>
<li>1.</li>
<li>2.</li>
<li>2.1</li>
<li>2.2</li>
<li>2.3</li>
<li>3.</li>
<li>3.1</li>
<li>3.2</li>
</ul>
I am using Microsoft SQL Server. I tried to use variables but it doesn't work the way I wanted to be. Here is my sample faulty output:
SELECT chart.col1,CASE
WHEN chart.CHART_LEVEL <= 2 THEN #no += 1
WHEN chart.CHART_LEVEL => 3 THEN CONCAT(#no,'.'#subNo += 1)
ELSE ''
END
AS 'RowNo'
FROM myTable chart
I am really sorry for giving insufficient details.

Answer 1

If you have a column in that table, that defines an order, you could get the section numbers with subqueries fetching the count of rows with lower ordered rows with the respective level.
Assuming the column defining the order is id something looking like this could be what you want.
SELECT col1,
convert(varchar(max), (SELECT count(*)
FROM myTable chart1
WHERE chart1.id <= chart.id
AND chart1.chart_level <= 2))
+
CASE
WHEN (SELECT count(*)
FROM myTable chart2
WHERE chart2.id <= chart.id
AND chart2.chart_level > 2
AND (SELECT count(*)
FROM myTable chart3
WHERE chart3.id <= chart.id
AND chart3.chart_level <= 2)
= (SELECT count(*)
FROM myTable chart4
WHERE chart4.id <= chart2.id
AND chart4.chart_level <= 2)) = 0
THEN ''
ELSE
'.' + convert(varchar(max), (SELECT count(*)
FROM myTable chart2
WHERE chart2.id <= chart.id
AND chart2.chart_level > 2
AND (SELECT count(*)
FROM myTable chart3
WHERE chart3.id <= chart.id
AND chart3.chart_level <= 2)
= (SELECT count(*)
FROM myTable chart4
WHERE chart4.id <= chart2.id
AND chart4.chart_level <= 2)))
END RowNo
FROM myTable chart;