How to update string values with incrementing numbers - sql

Question

I have a table that has a column which needs to be updated with values like
dummy1
dummy2
dummy3
..
..
..
dummy6
I created the following while loop script
create table people_test(UserName varchar(40))
GO
INSERT INTO people_test (UserName) values ('admin'),('test'),('opq'),('mn'),('ijkl'),('efgh'),('abcd')
GO
Select * from people_test
GO
DECLARE #i int;
DECLARE #j int = 1;
BEGIN
SELECT #i = COUNT(*) FROM people_test WHERE username <> 'admin';
WHILE(#j <= #i)
BEGIN
print 'i='+CONVERT(VARCHAR,#i)+' j='+CONVERT(VARCHAR,#j);
UPDATE people_test
SET
UserName = 'dummy'+ CONVERT(VARCHAR,#j)
WHERE username <> 'admin';
print 'i='+CONVERT(VARCHAR,#i)+' j='+CONVERT(VARCHAR,#j);
SET #j = #j + 1;
END;
END;
GO
Expected result
UserName
admin
dummy1
dummy2
dummy3
Result that I am seeing
UserName
admin
dummy6
dummy6
dummy6

Answer 1

You can solve this task with the row_number() function and therefore without a loop. Something like this:
drop table if exists #people_test
go
create table #people_test (UserName varchar (1000))
go
INSERT INTO #people_test (UserName) values ('admin'),('test'),('opq'),('mn'),('ijkl'),('efgh'),('abcd')
GO
update t
set t.UserName = 'dummy' + cast(t.rn as varchar(10))
from (
select row_number() over (order by UserName ) rn, *
from #people_test
where UserName!='admin'
) t
select * from #people_test
order by UserName

Answer 2

IF OBJECT_ID('tempdb..#TEMPS','U') IS NOT NULL
DROP TABLE #TEMPS
create table #TEMPS (UserName varchar(40))
GO
INSERT INTO #TEMPS (UserName) values ('admin'),('test'),('opq'),('mn'),('ijkl'),('efgh'),('abcd')
GO
UPDATE T1 SET T1.USERNAME= 'DUMMY'+CAST(T2.ROW AS varchar)
FROM #TEMPS AS T1, (SELECT ROW_NUMBER() OVER (ORDER BY USERNAME) AS ROW,* FROM #TEMPS ) AS T2
WHERE T2.UserName=T1.UserName AND T1.UserName!='ADMIN'
SELECT * FROM #TEMPS ORDER BY 1

Answer 3

Your own solution might work, but this is the wrong century for a CURSOR/LOOP based solution for such an easy task. Try something along this:
--Create a test table and fill it with data.
CREATE TABLE people_test(USERID INT IDENTITY,UserName VARCHAR(40))
GO
INSERT INTO people_test (UserName) VALUES
('admin')
,('test')
,('opq')
,('mn')
,('ijkl')
,('efgh')
,('abcd');
GO
SELECT * FROM people_test;
GO
--This is an updateable CTE
WITH upd AS
(
SELECT UserName
,CONCAT(UserName,ROW_NUMBER() OVER(ORDER BY USERID)) AS NewUserName
FROM people_test
WHERE UserName <> 'admin'
)
UPDATE upd SET UserName=NewUserName;
GO
--See the result
SELECT * FROM people_test;
GO
--Clean-up (carefull with real data!)
DROP TABLE people_test;
GO
The idea in short:
The CTE upd will return two columns:
UserName is the column you want to change
NewUserName is a computed column returning the value you want to see in UserName.
We can simply use UPDATE upd to update the underlying table.

Answer 4

create table people_test(USERID int,UserName varchar(40))
GO
INSERT INTO people_test (USERID, UserName) values (1,'admin'),(2,'test'),(3,'opq'),(4,'mn'),(5,'ijkl'),(6,'efgh'),(7,'abcd')
GO
Select * from people_test
GO
DECLARE #i int;
DECLARE #j int = 1;
DECLARE #k int;
DECLARE c_id cursor for
Select USERID from PEOPLE_TEST
WHERE username <> 'admin'
BEGIN
open c_id;
FETCH NEXT FROM c_id into #k
SELECT #i = COUNT(*) FROM PEOPLE_TEST WHERE username <> 'admin';
WHILE(#j <= #i)
BEGIN
UPDATE PEOPLE_TEST
SET
UserName = concat('dummy',#j)
WHERE userid = #k;
print 'i='+CONVERT(VARCHAR,#i)+' j='+CONVERT(VARCHAR,#j)+' k='+CONVERT(VARCHAR,#k);
SET #j = #j + 1;
FETCH NEXT FROM c_id into #k
END;
close c_id
Deallocate c_id
END;
Select * from people_test
GO