Change phone number format - asp.net

Question

I have phone number field in database. It has already data.
I want to change my phone number format to "XXX-XXX-XXXX"
Current database has no any phone format.
So there may be garbage data. I have already applied validation for new records but now I want to change my existing data also.
Is there any specific way through that I can change my existing data. And make all phone numbers to follow this format.
Please advice.

Answer 1

Create function to remove the non-numeric data and do the formatting
CREATE FUNCTION [UDF_STRIP_NONNUMERIC_DATA](#str VARCHAR(8000))
RETURNS VARCHAR(8000)
AS
BEGIN
WHILE Patindex('%[^0-9]%', #str) > 0
BEGIN
SET #str = Stuff(#str, Patindex('%[^0-9]%', #str), 1, '')
END
RETURN #str
END
You can use STUFF function to inset the - between phone number
Select left(Stuff(Stuff(dbo.[UDF_STRIP_NONNUMERIC_DATA](Phone),4,0,'-'),8,0,'-'),12)
From yourtable
If you are using SQL SERVER 2012+ use can use FORMAT function (thanks to LukStorms, who mentioned it in comment)
SELECT Format(Cast(dbo.[Udf_strip_nonnumeric_data](Phone) AS BIGINT), '###-###-####')
FROM yourtable
To update
Update yourtable
SET phone = left(Stuff(Stuff(dbo.[UDF_STRIP_NONNUMERIC_DATA](Phone),4,0,'-'),8,0,'-'),12)
Demo
declare #str varchar(100)= '9225-123-4567'
select left(Stuff(Stuff(dbo.[UDF_STRIP_NONNUMERIC_DATA](#str),4,0,'-'),8,0,'-'),12)
Result : 922-512-3456

Answer 2

declare #phone varchar(24)
set #phone = '[phone]'
--set #phone = '314789-4532'
--set #phone = '3457894532'
--set #phone = '534-789-4532'
SELECT
LEFT(N,3) + '-' + SUBSTRING(N,4,3) + '-' + RIGHT(N,4)
FROM
(SELECT CAST(CAST((
SELECT SUBSTRING(#phone, Number, 1)
FROM master..spt_values
WHERE Type='p' AND Number <= LEN(#phone) AND
SUBSTRING(#phone, Number, 1) LIKE '[0-9]' FOR XML Path(''))
AS xml) AS varchar(MAX)) as N) as N

Answer 3

Ok, to replace all non-numeric characters, look at this.
Here is a sample script (copied from that link) to show you how it works (You'll need to modify this to fit your table name and column names:
-- Step 1: creates table to use to hold every char in every phone number
if object_id('dbo.tally') is not null drop table dbo.tally
select top 10000 --change to fit max length of phone number
identity(int,1,1) as n
into dbo.tally
from master.dbo.syscolumns sc1,
master.dbo.syscolumns sc2
-- add pk to maximize performance
alter table dbo.tally
add constraint pk_tally_n
primary key clustered (n) with fillfactor = 100
-- Step 2: Create temporary table holding three bad phone numbers
declare #phonetable table
(uniqueid int identity(1,1),
phone_number varchar(500))
insert into #phonetable (phone_number)
select '01234-567-890' union
select '012345 6789ext' union
select 'n/a' union select '...12345.....';
-- Step 3: identify, for every character, whether it is a number or not,
and remove the non-numeric ones
with cte (uniqueid, phone_number, goodchar, badchar) as
( select uniqueid, phone_number,
case when substring(phone_number,N,1) not like '%[^0-9]%'
then substring(phone_number,N,1) end as goodchar,
case when substring(phone_number,N,1) like '%[^0-9]%'
then substring(phone_number,N,1) end as badchar
from #phonetable , Tally
where phone_number like '%[^0-9]%' and N <= len(phone_number) )
select distinct phone_number,
isnull( stuff (
( SELECT '' + goodchar
FROM cte t1
where t1.UniqueID = t2.UniqueID
FOR XML PATH ( '' ) ) , 1 , 0 , '' ) ,'')
as clean_phone_number from cte t2
to display the numbers with formatting, just extract the appropriate pieces and re-concatenate them with the dashes.
Select case len(phone)
When 10 then left(phone, 3) + '-' +
substring(phone, 4,3) + '-' +
substring(phone, 7,4)`
When 7 then left(phone, 3) + '-' +
substring(phone, 4,4)
Else '' end
To create a computed column
Alter table Add Column FormattedPhone as
case len(phone)
When 10 then left(phone, 3) + '-' +
substring(phone, 4,3) + '-' +
substring(phone, 7,4)`
When 7 then left(phone, 3) + '-' +
substring(phone, 4,4)
Else '' end

Answer 4

If you don't mind a UDF
Select [dbo].[udf-Str-Format-Phone]('334)789-4532')
Returns
334-789-4532
The UDF
CREATE FUNCTION [dbo].[udf-Str-Format-Phone] (#S varchar(max))
Returns varchar(25)
AS
Begin
Declare #Return varchar(25)
;with cte0(N) As (Select 1 From (Values(1),(1),(1),(1),(1)) N(N))
, cteN(N) As (Select Top (Len(#S)) Row_Number() over (Order By (Select NULL)) From cte0 N1, cte0 N2)
, cteS(S) As (Select Substring(#S,N,1) From cteN Where Substring(#S, N, 1) LIKE '[0-9]' FOR XML Path(''))
Select #Return = IIf(Len(S)>=10,Stuff(stuff(S,4,0,'-'),8,0,'-'),Stuff(S,4,0,'-')) From cteS
Return #Return
End
-- Syntax : Select [dbo].[udf-Str-Format-Phone]('[phone]') -- Returns 334-789-4532
-- Syntax : Select [dbo].[udf-Str-Format-Phone]('Phone:[phone]') -- Returns 789-4532