Cannot find the right SQL dialect: "case when" .. fails

Hello !

Though I cannot make dependend fields working - have to omit a space, if one
field contains null - so, I do not have to omit the filed itself. Cocatenating fields in
the true/false fields for a condition does not work.

So I thought, make a query/view and build the field completely
in sql. So I have this:

"Sheet1"."NAMENSPREF,C,3" as "b", --see the data
"Sheet1"."STRASSE,C,25" as "d",
case when ("Sheet1"."NAMENSPREF,C,3" is not null) then "Name" = 'aa'
	else "Name" = 'bb'


But I am getting these errors:

SQL Status: HY000
Error code: 1000

syntax error, unexpected $end, expecting BETWEEN or IN or SQL_TOKEN_LIKE

If I do the query like this:

"Sheet1"."NAMENSPREF,C,3" as "b",
"Sheet1"."STRASSE,C,25" as "d",
case when ("Sheet1"."NAMENSPREF,C,3" is not null) then 'aa'
	else 'bb'
	end as "Name"


I get no data for the field, although I see, that this data exists.

I hope to get a little help. I am using a ODB, which i made from ODS.
I cannot find which dialect is right.
BTW, I tried both, hitting F5 in the designer and using sql direct.

Any help would be great.

Thanks anyway and
best regards,