Doesnt display the right count in dynamic sql - sql

Question

Here is the input table
I cannot get the right count of the sku. I need to achieve this by this dynamic sql. It gives result like below:
SET #SQL = 'SELECT DISTINCT
a.'+#primary_column+' AS [No. of distinct'' '+#primary_column+']
,sum(case when '+#secondary_column+' is null or '+#secondary_column+' = '''' then 0 else 1 end) AS ''Total_Count''
,STUFF((SELECT DISTINCT '', ['' +'+#secondary_column+'+'']''
FROM ['+#TableName+'] b
WHERE b.'+#primary_column+' = a.'+#primary_column+'
FOR XML PATH('''')),1, 1, '''') AS '+#secondary_column+'
FROM ['+#TableName+'] a
GROUP BY '+#primary_column+'';
PRINT(#SQL)
EXEC(#SQL)
This is the expected output

Answer 1

Change this:
,sum(case when '+#secondary_column+' is null or '+#secondary_column+' = '''' then 0 else 1 end) AS ''Total_Count''
On this:
,COUNT(DISTINCT NULLIF('+#secondary_column+'','''')) ''Total_Count''
Full query:
DECLARE #sql nvarchar(max),
#secondary_column nvarchar(max) = 'Parent_sku',
#primary_column nvarchar(max) = 'category',
#TableName nvarchar(max) = 'SomeTable'
SELECT #sql = '
SELECT ' + #primary_column + ' AS [No. of distinct'' ' + #primary_column+ '],
COUNT(DISTINCT ' + #secondary_column + ','''')) Total_count,
STUFF((SELECT DISTINCT '','' + QUOTENAME(ISNULL(' + #secondary_column + ',''''))
FROM ' + #TableName + ' s
WHERE s.' + #primary_column+ ' = a.' + #primary_column+ '
FOR XML PATH('''')),1,1,'''') as ' + #secondary_column + '
FROM ' + #TableName + ' a
GROUP BY ' + #primary_column
PRINT #sql
EXEC sp_executesql #sql
Output:
No. of distinct' category Total_count Parent_sku
1 [TB004]
Kids 1 [TB003]
Men 1 [TB001]
Women 1 [TB002]
EDIT
F.e. I got this as input:
('TB001L', 'TB001', 20, 'AQW2342S', 'Men'),
('TB001S', 'TB001', 21, 'GQW2342S', 'Men'),
('TB002M', 'TB002', 22, 'ZQW2342S', 'Women'),
('TB002S', 'TB002', 23, 'BQW2342S', 'Women'),
('TB003M', 'TB003', 20, 'KQW2342S', 'Kids'),
('TB003S', 'TB003', 23, 'RQW2342S', 'Kids'),
('TB005S', NULL, 22, 'RQW2342S', ''),
('TB005XL', NULL, 23, 'JQW2342S', '')
2 last rows is with NULL in #secondary_column. Output will be:
No. of distinct' category Total_count Parent_sku
0 []
Kids 1 [TB003]
Men 1 [TB001]
Women 1 [TB002]