Help needed: How to update a BYTE Field by another table

Hello, I am a little bit frustrated because I want to copy / create a table with a BYTE field. The normal insert command does not work because i must use a distinct clause in the select statement: insert into tab_a ( a,b,f,g, BYTE_field ) select distinct a,b,f,g , BYTE_field from tab_b where .... Results in Error: -613 Blobs are not allowed in the "distinct" clause. and do first an insert without the BYTE_Field and do then an additionally update does not work either: update tab_a set BYTE_Field = ( select BYTE_Field from tab_b where tab_b.index = tab_a.index); Result in Error: 9931: Byte and Text datatypes in row and collection types not allowed. Can anyone help and has a solution for me. Thanks Thorsten