Question

I have a complex nested replace which I am using to join two tables in MSSQL.

select * from A
  left outer join 
select * from B
on
  replace(
     replace(
        replace(
           replace(
              replace(A.Column1, '1114', ''),
             '1160', ''), 
          '1162', ''),
        '1167', ''),
      '1176', ''),
    '1177', '')  = B.Column1

The whole reason I am doing this is because data in Table1 contains of some noise – numbers like 1160, 1162 etc wheres Table2 is clean characters.

Eg. - Table 1 - 'HELLO1160WORLD'
      Table 2 - 'HELLOWORLD'

Now in my situation I should be able to match them as one entry.

My current approach of nested replace does work but I am not convinced that this is an elegant way to do this. Any help will be much appreciated. Thanks

Answer 1

The problem is that T-SQL does not easily allow to mark expressions with a name so you can refer to them from a different place. There is a way to do this though:

select replaceN
from T
cross apply (select replace1 = replace(T.col, 'x', 'y')) r1
cross apply (select replace2 = replace(replace1, 'x', 'y')) r2
cross apply (select replace3 = replace(replace2, 'x', 'y')) r3
...

This at least gets rid of the crazy nesting. It has no negative performance impact.