cannot parse alias table objects (database DB2)

[bodev]

Hi,
my environment: BO XI 3.1
database: DB2

I have aliased a table (fairly large) and wanted to create objects that check condition in this alias table and another table before bringing data from this alias table, but I get below error when I try to parse:

Parse failed: Exception: DBD, [IBM][CLI Driver][DB2/AIX64] SQL0206N
"<schema>.<Alias_table>.<Column_name>" is not valid in the context where it is used. SQLSTATE=42703 State: 42S22

the object contains code something like:

case when table2.column='ABC' and Alias_table.column1 ='X' then
Alias_table.column2

Please help.