SQL串联查询

Question

I have a column called I_Tags and im trying to compare it to another table Asset_Tags .

I_Tags has fields like

PV-B02-0115
B04-PV-7126B--
B05-PV0841A--
B05-PV-0841B--
B09-PV-1155A--

Asset_Tags have fields like

PV-B04-6888
PV-B05-0841A--
PV-B05-1219
PV-B09-1155A--

Im unsure how to write a case statement based on the following scenarios:

1. If the first two characters in I_Tag are letters PV, match the entire string for matches with Asset_Tags
2. If not, and PV is 4th & 5th characters in I_Tag , move them to the 1st & 2nd character locations and remove any/all number of the dashes (-) at the end and match with Asset_Tags .

I have never written a case statement in SQL so Im unsure how to write a query for this.

Any help would be appreciated. Thank you

Answer 1

Maybe this helps, if returns the result so that PV is always at the start and removes the trailing -s:

select
  case 
    when I_Tags like 'PV%' then I_Tags
    when I_Tags like '____PV%' then
      'PV-'+left(I_Tags, 3) + 
      substring(I_Tags, 7, len(I_Tags) -5 -patindex('%[^-]%', reverse(I_Tags)))
    end as test
from
  table1

You can test it in SQL Fiddle: http://sqlfiddle.com/#!6/526db/16

Not sure if there was a typo in your example with B05-PV0841A--, but it leaves it without the -.