Retrieve oracle table record issue

i have a table called “case” with a column datatype is CHAR(4 Byte) called “case_code”. it is primary key column. Also in my controller class, it has a actionView method, inside it i use

Case::findOne([‘case_code’ => ‘abc’]) but it return null. i have a row with case_code is abc inside this table, but when i retrieve it by Case::findOne([‘case_code’ => 'abc ']), it return the ActiveRecord.

Anyone know what happen ? Thank a lot…