Optimization of a substring query with charindex to trim the left part of a string - sql

Question

I need to get a substring of xyzdf/1234 resulting in 1234 (i.e. trimming the left part of the slash / ) . I have used
substring('xyzdf/1234',charindex('/','xyzdf/1234')+1,len('xyzdf/1234')-charindex('/','xyzdf/1234'))
which works but it is repetitive...
then I have used this way:
stuff('xyzdf/1234',1,charindex('/','xyzdf/1234'),'') and it works too and it is more compact, but still repeats the same argument twice 'xyzdf/1234'.
I wonder what would be the faster way to trim the left part. I will need to clean data in one column for million records. Not sure if the stuff command is faster enough. (Mind you it is a bulk operation). Thanks!

Answer 1

You could select the string from a VALUES.
That way you can repeat the value without double hardcoding it.
Then get the right part with the number from it.
F.e. using RIGHT, CHARINDEX, REVERSE and VALUES:
select right(val, charindex('/',reverse(val))-1) as nr
from (values ('xyzdf/1234')) q(val);
Or use SUBSTRING, CHARINDEX, LEN and VALUES:
select substring(val,charindex('/',val)+1,len(val)) as nr
from (values ('xyzdf/1234')) q(val);
Or abuse PARSENAME:
select parsename(replace('xyzdf/1234','/','.'),1) as nr;
Or use variables:
declare #value varchar(30) = 'xyzdf/1234';
declare #nr int = right(#value, charindex('/',reverse(#value))-1);
select #nr as nr;
But if the intention is to update a column so that only the number remains?
Then using the SUBSTRING method is probably still the safest.
Because it would keep those without / untouched, and without crashing on an Invalid length parameter passed error.
Example:
declare #Table table (id int identity(1,1) primary key, col1 varchar(30));
insert into #Table (col1) values
('xyzdf/1234'),
('12345');
update #Table
set col1 = substring(col1,charindex('/',col1)+1,len(col1))
where col1 like '%/[0-9]%';
select * from #Table;