Add SQL SELECT COUNT result to an existing column as text - sql

Question

I have two tables:
1. TABLE [dbo].[ItemCategories](
[Id] [int] IDENTITY(1,1) NOT NULL,
[CategoryId] [int] NULL,
[StockId] [int] NULL,
2. TABLE [dbo].[Categories](
[Id] [int] IDENTITY(1,1) NOT NULL,
[ParentCategoryId] [int] NULL,
[CategoryName] [nvarchar](100) NULL,
[Slug] [nvarchar](150) NULL
And this query in SQL Server 2012
SELECT [CategoryName], [Slug], [ParentCategoryId], [Id]
FROM [Categories]
ORDER BY [ParentCategoryId] DESC
Which returns these rows
[CategoryName] [Slug] [ParentCategoryId] [Id]
Exercise exercise 42 46
Fashion fashion 42 47
And I have a second query:
SELECT COUNT(*)
FROM [ItemCategories]
WHERE CategoryId = '46' <--- This Id is the same as [Id] from the first query
How can I a modify the first query to add total count from the second query to the returned CategoryName column (as a single string) ?
Like this:
[CategoryName] [Slug] [ParentCategoryId] [Id]
Exercise (31) exercise 42 46
Fashion (56) fashion 42 47
I have created this join, but I don't know how to add the COUNT(*) as text
SELECT [CategoryName], [Slug], [ParentCategoryId], [Categories].[Id]
FROM [Categories]
INNER JOIN [ItemCategories] ON [Categories].[Id]=[ItemCategories].[CategoryId]
ORDER BY [ParentCategoryId] DESC

Answer 1

You can use the count(*) window function. I would put it in a separate column, but you can do:
SELECT [CategoryName] + ' (' + cast(count(*) over (partition by Id) as varchar(255)) + ')',
[Slug], [ParentCategoryId], [Id]
FROM [Categories]
ORDER BY [ParentCategoryId] DESC;
EDIT:
For two tables, use a JOIN and GROUP BY:
SELECT c.CategoryName + ' (' + cast(count(ic.Id) as varchar(255)) + ')',
c.Slug, c.ParentCategoryId, c.Id
FROM Categories c LEFT JOIN
ItemCategories ic
on ic.CategoryId = c.Id
GROUP BY c.CategoryName, c.slug, c.ParentCategoryId, c.id
ORDER BY ParentCategoryId DESC;