How to decrement a number in a character-separated string

I have strings in a SQL Server table column:

I have to reduce the last digits after hyphen by one (as shown here):

Any help?

Try this fugliness. While not recommended, it seems to work. A proper database design is what is needed, for obvious performance and coding issues. The Common Table Expression just sets up test data and is a great way to provide example data. You really only need to select the last "joined_back" but I included the separate parts for completeness. Adapted from this post and he should get any credit: https://stackoverflow.com/a/20369450/2543416

with tbl(SequenceId) as (
  select '2-10-14' union all
  select '2-8-15' union all
  select '2-8-16' union all
  select '2-8-16' union all
  select '2-17-21' union all
  select '2-0-5'
)
select 
 LEFT(SequenceId, LEN(SequenceId) - CHARINDEX('-',REVERSE(SequenceId))+1) AS first_part,
 RIGHT(SequenceId, CHARINDEX('-',REVERSE(SequenceId))-1) AS second_part,
 RIGHT(SequenceId, CHARINDEX('-',REVERSE(SequenceId))-1) - 1 as decrement,
 LEFT(SequenceId, LEN(SequenceId) - CHARINDEX('-',REVERSE(SequenceId))+1) + cast(RIGHT(SequenceId, CHARINDEX('-',REVERSE(SequenceId))-1) - 1 as char(2)) as joined_back 
from tbl;


first_part  second_part decrement   joined_back
2-10-       14          13          2-10-13
2-8-        15          14          2-8-14
2-8-        16          15          2-8-15
2-8-        16          15          2-8-15
2-17-       21          20          2-17-20
2-0-        5           4           2-0-4 

It could also be written like this which aids in troubleshooting:

with tbl(SequenceId) as (
  select '2-10-14' union all
  select '2-8-15' union all
  select '2-8-16' union all
  select '2-8-16' union all
  select '2-17-21' union all
  select '2-0-5'  union all
  select null
),
tbl_splitup(first_part, second_part, decrement) as (
  select LEFT(SequenceId, LEN(SequenceId) - CHARINDEX('-',REVERSE(SequenceId))+1),
    RIGHT(SequenceId, CHARINDEX('-',REVERSE(SequenceId))-1),
    RIGHT(SequenceId, CHARINDEX('-',REVERSE(SequenceId))-1) - 1 as decrement
  from tbl
)
-- select * from tbl_splitup
select first_part + cast(decrement as char(2)) as joined_back 
from tbl_splitup;