Issue In Changing Column Names using SQL Server - sql

Question

It's my first question on Stack Overflow; I am facing a problem in changing column names.
I have a table INS_Sink with columns like
INS2017, INS2018, INS2019, INS2020
Now I need to change the existing column names like this:
INS2017 to INS CY-3,
INS2018 to INS CY-2,
INS2019 to INS CY-1,
INS2020 to INS CY,
where CY = CurrentYear.
I need to change all the columns dynamically like the above mentioned and the column names should be changed automatically when the year gets changed like in the year 2021, INS2020 should become INS CY-1..
Can anyone help me how to achieve this and I don't want to alter my columns here?
Thanks in advance...

Answer 1

First, you should not do this. The underlying table should reflect the correct data.
Second, you should not use names like INS CY-1. Such a name needs to be escaped. Instead, you should use INS_CY_1. That is cleaner.
Next, you have a problem with your data model. You should be storing the data as:
YEAR INSVALUE
2017 ?
2018 ?
Of course, you might have other columns that you haven't specified.
With this data structure, it is easy to create a view that does what you want. Say, the current year is found using YEAR(GETDATE()). Then:
select sum(case when t.year = v.yyyy then t.insvalue end) as ins_cy,
sum(case when t.year = v.yyyy - 1 then t.insvalue end) as ins_cy_1,
sum(case when t.year = v.yyyy then t.insvalue end) as ins_cy_2
from t cross join
(values (year(getdate())) v(yyyy);
You can continue this logic for however many years you want to go back in time.

Answer 2

if you really need to get the data in CY-xyz columns then it might be better to create a view and adjust the view when needed (you could use both the view and the table for DML operations).
create table dbo.INS_Sink_test
(
id int identity(1,1) constraint pk_id_ins_sink_test primary key clustered,
col1 int,
col2 int,
INS2010 int,
INS2011 int,
INS2012 int,
INS2013 int,
INS2014 int,
INS2015 int,
INS2016 int,
INS2017 int,
INS2018 int,
INS2019 int,
INS2020 int
)
go
insert into dbo.INS_Sink_test
(
col1, col2, INS2010, INS2011, INS2012, INS2013, INS2014, INS2015, INS2016, INS2017, INS2018, INS2019, INS2020
)
values
(1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4)
go
--create/adjust a view
declare #year smallint = year(getdate());
newyear:
declare #colssql nvarchar(max) = N'';
select #colssql = #colssql + N',' + quotename(name) + ' as ' + quotename(newcolname)
from
(
select column_id,
name,
case when name like 'INS[0-9][0-9][0-9][0-9]' then 'CY' + isnull(cast(nullif(cast(replace(name, 'INS', '') as smallint)-#year, 0) as sysname), '')
else name
end as newcolname
from sys.columns
where object_id = object_id('dbo.INS_Sink_test')
) as a
order by column_id;
declare #viewsql nvarchar(max) = N'view dbo.v_INS_Sink_test
as
select
' + stuff(#colssql, 1, 1, N'') + N'
from dbo.INS_Sink_test
';
select #viewsql = case when object_id('dbo.v_INS_Sink_test') is null then N'create' else N'alter' end + N' ' + #viewsql ;
--print #viewsql
exec(#viewsql);
--dont forget to refresh other views that depend on v_ins_sink_test
--exec sp_refreshview 'dbo.view_xyz';
exec sp_refreshview 'dbo.v_INS_Sink_test';
select #year as theyear;
select *
from dbo.INS_Sink_test;
select *
from dbo.v_INS_Sink_test;
if #year = 2021
begin
--cleanup
if object_id('dbo.INS_Sink_test') is not null
begin
drop table dbo.INS_Sink_test;
end
if object_id('dbo.v_INS_Sink_test') is not null
begin
drop view dbo.v_INS_Sink_test;
end
return;
end
--i know what you did in 2021..
select #year = 2021;
goto newyear
--cleanup
/*
if object_id('dbo.INS_Sink_test') is not null
begin
drop table dbo.INS_Sink_test;
end
if object_id('dbo.v_INS_Sink_test') is not null
begin
drop view dbo.v_INS_Sink_test;
end
*/
For changing the column names of the table:
create table dbo.INS_Sink_test
(
id int identity(1,1) constraint pk_id_ins_sink_test primary key clustered,
col1 int,
col2 int,
INS2010 int,
INS2011 int,
INS2012 int,
INS2013 int,
INS2014 int,
INS2015 int,
INS2016 int,
INS2017 int,
INS2018 int,
INS2019 int,
INS2020 int
)
go
insert into dbo.INS_Sink_test
(
col1, col2, INS2010, INS2011, INS2012, INS2013, INS2014, INS2015, INS2016, INS2017, INS2018, INS2019, INS2020
)
values
(1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4)
go
select *
from dbo.INS_Sink_test
go
--rename columns
declare #year smallint = year(getdate());
declare #renamecolssql nvarchar(max) = N'';
select #renamecolssql = #renamecolssql + N'exec sp_rename ''' + quotename(object_schema_name(object_id)) + N'.' + quotename(object_name(object_id)) + N'.' + quotename(name) + ''', '+ quotename(newcolname) + '; '
from
(
select
object_id,
column_id,
name,
'INS CY' + isnull(cast(nullif(cast(replace(name, 'INS', '') as smallint)-#year, 0) as sysname), '') as newcolname
from sys.columns
where object_id = object_id('dbo.INS_Sink_test') --<-- change the name of the table
and name like 'INS[0-9][0-9][0-9][0-9]'
) as a
order by column_id;
exec(#renamecolssql);
go
select *
from dbo.INS_Sink_test
go
--cleanup
drop table dbo.INS_Sink_test
go