How to format a numeric column as phone number in SQL

Question

I have table in the database with a phone number column. The numbers look like this:

123456789

I want to format that to look like this:

Answer 1

Solutions that use SUBSTRING and concatenation + are nearly independent of RDBMS. Here is a short solution that is specific to SQL Server:

declare @x int = 123456789
select stuff(stuff(@x, 4, 0, '-'), 8, 0, '-')