3548890 - Unexpected behavior when enabling "streamlined dynamic SQL"- SAP ASE

• if @a is null will be raised Error 403 if @a is a text tyep.
  
  1> declare @a text
  2> set @a=null
  3> if @a is null
  4>   select 1
  5> else
  6>   select -1
  7> go
  Msg 403, Level 16, State 2:
  Server 'BK9', Line 3:
  Invalid operator for datatype op: is null type: TEXT.
  
  
• But when enabling "streamlined dynamic SQL", it's not raised Error 403 and return unexpected behavior when assigning a return value of case when.
  
  1.if is null
  

  1> declare @a text
  2> set @a=null
  3> if @a is null
  4>   select 1
  5> else
  6>   select -1
  7> go
  (1 row affected)

   -----------
             1

  (1 row affected)
  1>

  
  2.case when : refer to "Reproducing the Issue" for detail repro steps
  
  

  1> declare @t1 text, @t2 text, @t text
  2> select @t = case when t2.id is null then t1.t1 else t2.t2 end, @t1=t1.t1,@t2=t2.t2
  3> from #table1 t1
  4> left outer join #table2 t2 on t2.id = t1.id
  5>
  6> if @t1 is null
  7> select '@t1 is null'
  8> else
  9> select '@t1 is not null'
  10>
  11>
  12> if @t2 is null
  13> select '@t2 is null'
  14> else
  15> select '@t2 is not null'
  16>
  17> if @t is null
  18> select '@t is null'
  19> else
  20> select '@t is not null'
  21>
  22> go
  (1 row affected)

   -----------
   @t1 is null

  (1 row affected)

   -----------
   @t2 is null

  (1 row affected)

   --------------
   @t is not null            <<<wrong return value

  (1 row affected)
  1>

  
  
  

SAP Adaptive Server Enterprise (ASE)

text datatype, case when, unexpected behavior, Msg 403, CR830181, CR#830181, 830181 , KBA , BC-SYB-ASE , Sybase ASE Database Platform (non Business Suite) , Problem