sql server - Is it possible to do a join on a user-calculated/custom SQL view column? -


this sql server

so have sql view manually define values of custom column via case statement. let's call column name statusid.

now, have mapping table holds statusid , description. let's call table dbo.statusmapping. possible join on statusmapping.statusid , custom view column "statusid" can obtain description can add view?

example code:

select     distinct(a.overallid),     case         when a.istrue null 1 else 2     end statusid, --this i'm trying join table on     b.description dbo.[maintable] join dbo.[statusmapping] b on b.statusid = statusid --this fails. "invalid column name 'statusid'"

you have several options join:

  • repeat expression computed column in where clause - not ideal, because same expression repeated, or
  • use common table expression - work sql server, not work in mysql , other rdbms not support cte, or
  • make nested select table alias - lets avoid repetition.

here example of how use nested select:

select     distinct(x.overallid),     x.statusid,     b.description (     select         a.overallid,         case             when a.istrue null 1 else 2         end statusid     dbo.[maintable] ) x join dbo.[statusmapping] b on b.statusid = x.statusid

note: not sure of purpose of distinct around a.overallid in original query. copied mechanically query, chances going unnecessary, or need replace group by.


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