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

I do not recommend keeping bad data in the database and then only correcting it on the output. We have a database where phone numbers are entered in variously as :

• (555) 555-5555
• 555+555+5555
• 555.555.5555
• (555)555-5555
• 5555555555

Different people in an organization may write various retrieval functions and updates to the database, and therefore it would be harder to set in place formatting and retrieval rules. I am therefore correcting the data in the database first and foremost and then setting in place rules and form validations that protect the integrity of this database going forward.

I see no justification for keeping bad data unless as suggested a duplicate column be added with corrected formatting and the original data kept around for redundancy and reference, and YES I consider badly formatted data as BAD data.