SQL Server 2019 (Linux)

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CREATE TABLE PersonsInitial (
    tel varchar(255),
    firstname varchar(255),
    lastname varchar(255)
);

insert into PersonsInitial(tel, firstname, lastname) values
('+41/ jfakl2 eaf3efa54844','Manu','Johns'),
('01-afe fa-e8fa5a +e5+ e+234','Fernand','Wajk'),
(' +41/34 jfakl2 eaf3efa54844','Fred','Johns');
3 rows affected

CREATE FUNCTION dbo.fnCleanTel (@Input VARCHAR(255))
RETURNS VARCHAR(255)
AS
BEGIN
  DECLARE @Output VARCHAR(255) = LTRIM(RTRIM(@Input));
  
  IF LEFT(@Output, 1) = '+'
    SET @Output = STUFF(@Output,1,1,'00');
    
  WHILE PATINDEX('%[^0-9]%', @Output) > 0
    SET @Output = REPLACE(@Output, SUBSTRING(@Output,PATINDEX('%[^0-9]%',@Output),1),'');
  
  RETURN @Output;
END;
CREATE TABLE PersonsFinal (
    tel varchar(255),
    firstname varchar(255),
    lastname varchar(255)
);
insert into PersonsFinal (tel, firstname, lastname) 
select dbo.fnCleanTel(tel) as clean_tel, firstname, lastname 
from PersonsInitial;
3 rows affected

select tel, firstname, lastname from PersonsFinal


tel
firstname
lastname


00412354844
Manu
Johns

01855234
Fernand
Wajk

0041342354844
Fred
Johns

tel	firstname	lastname
00412354844	Manu	Johns
01855234	Fernand	Wajk
0041342354844	Fred	Johns