Replacing more than 1 period to 1 period in sql - sql

Question

I have the following code to convert more than one period to one period in a column of a table.
alter proc replace_characters_1
#COLUMN_NAME varchar(30),
#TABLE_NAME varchar(30)
as
declare #SQL varchar(MAX)
while #COLUMN_NAME like '%..%'
begin
set #SQL= 'update [' +#TABLE_NAME+ '] set [' +#COLUMN_NAME+ '] = replace([' +#COLUMN_NAME+ '],''..'',''.'')';
exec(#SQL)
end
I want to change the Anna...Amal to Anna.Amal with one go, but the loop is not working. What should I do?`

Answer 1

One possible approach is to use nested REPLACE()s:
SET ColumnName = REPLACE(REPLACE(REPLACE(ColumnName, '.', '<>'), '><', ''), '<>', '.')
After the first REPLACE() the part from the text that contains periods (.) looks like <><><>. After the second REPLACE() the result is only <> and the final REPLACE() returns single period (.). If the characters < and > exist in the input text, you can choose another pair of characters.
Table:
CREATE TABLE Data (Name varchar(100))
INSERT INTO Data (Name)
VALUES
('ANNA..Amal'),
('ANNA..Amal.'),
('ANNA.Amal.'),
('ANNA...........Amal.'),
('ANNA.....Amal')
Procedure:
CREATE PROC replace_characters_1
#COLUMN_NAME sysname,
#TABLE_NAME sysname
AS
BEGIN
DECLARE #SQL nvarchar(MAX)
DECLARE #RC int
SET #SQL =
N'UPDATE ' + QUOTENAME(#TABLE_NAME) + N' ' +
N'SET ' + QUOTENAME(#COLUMN_NAME) + N' = ' +
N'REPLACE(REPLACE(REPLACE(' + QUOTENAME(#COLUMN_NAME) + ', ''.'', ''<>''), ''><'', ''''), ''<>'', ''.'') ' +
N'WHERE ' + QUOTENAME(#COLUMN_NAME) + N' LIKE ''%..%'''
EXEC #RC = sp_executesql #SQL
RETURN #RC
END
Result:
EXEC replace_characters_1 N'Name', N'Data'
SELECT * FROM Data
Name
ANNA.Amal
ANNA.Amal.
ANNA.Amal.
ANNA.Amal.
ANNA.Amal

Answer 2

Here is an approach that will reduce repeating characters.
Example
Declare #YourTable Table ([SomeCol] varchar(50))
Insert Into #YourTable Values
('Anna...Amal')
,('Anna........Amal')
,('Anna.Amal')
,('Anna Amal')
Select *
,NewVal = replace(replace(replace(SomeCol,'.','†‡'),'‡†',''),'†‡','.')
from #YourTable
Returns
SomeCol NewVal
Anna...Amal Anna.Amal
Anna........Amal Anna.Amal
Anna.Amal Anna.Amal
Anna Amal Anna Amal

Answer 3

Please check Zhorov's answer as it avoids multiple operations like this one.
CREATE PROCEDURE replace_characters_1
#COLUMN_NAME varchar(30),
#TABLE_NAME varchar(30)
AS
BEGIN
DECLARE #SQL NVARCHAR(MAX) = N'
UPDATE T SET
' + QUOTENAME(#COLUMN_NAME) + N' = REPLACE(' + QUOTENAME(#COLUMN_NAME) + N',''..'',''.'')
FROM
' + QUOTENAME(#TABLE_NAME) + N' AS T
WHERE
T.' + QUOTENAME(#COLUMN_NAME) + N' LIKE ''%..%'';
SET #UpdatedRowsOut = ##ROWCOUNT;';
DECLARE #UpdatedRows INT = 1;
WHILE #UpdatedRows > 0
BEGIN
EXECUTE sp_executesql
#SQL,
N'#UpdatedRowsOut INT OUTPUT',
#UpdatedRowsOut = #UpdatedRows OUTPUT;
END
END
Dynamic SQL is now returning the amount of rows that were updated, so it keeps going as long as there are values with .. for that column (note that there is a WHERE filter, you don't want to update all rows every time!).
SQL Server isn't the best for regex expressions, maybe you want to consider using a CLR function if you need to do different kind of stuff with regex.

Answer 4

I am using CHARINDEX and STUFF to derive the resultset
DECLARE #sqlstring Varchar(max) = 'Anna...Amal'
-- Getting first index of .
DECLARE #firstidx INT = CHARINDEX('.',#sqlstring)
-- Getting last index of .
Declare #lastidx int = (LEN(#sqlstring) - CHARINDEX('.',REVERSE(#sqlstring))) + 1
-- Stuffing the gap with emptystring
SELECT STUFF(#sqlstring,#firstidx+1,(#lastidx-#firstidx),'') as result
Result
+-----------+
| result |
+-----------+
| Anna.Amal |
+-----------+
UPDATE: If there are multiple comma separated values
DECLARE #sqlstring Varchar(max) = 'Anna...Amal,Vimal...Mathew'
SELECT STRING_agg(removedvalues,',') as values
FROM
(SELECT STUFF(value, CHARINDEX('.',value)+1
,(LEN(value) - CHARINDEX('.',REVERSE(value)) + 1) - CHARINDEX('.',value),'') AS removedvalues
FROM string_split(#sqlstring,',') ) AS t
+------------------------+
| Values |
+------------------------+
| Anna.Amal,Vimal.Mathew |
+------------------------+