Convert stored string into sql expression

Hello Guru,

Having data below

create table XDATA (OD VARCHAR(2),DOCID NUMBER(10),CODE VARCHAR(5), CTN VARCHAR(5));

create table XMAP (OD VARCHAR(2),CODE_IN VARCHAR(15), CTN_IN VARCHAR(15));

Insert into XDATA (OD,DOCID,CODE,CTN) values ('W1',1,'STA','CC');

Insert into XDATA (OD,DOCID,CODE,CTN) values ('W1',2,'STA','CD');

Insert into XDATA (OD,DOCID,CODE,CTN) values ('W1',3,'HIG','CC');

Insert into XDATA (OD,DOCID,CODE,CTN) values ('W1',4,'HIG','CD');

Insert into XDATA (OD,DOCID,CODE,CTN) values ('W1',5,'EME','CC');

Insert into XDATA (OD,DOCID,CODE,CTN) values ('W1',6,'EME','CD');

Insert into XDATA (OD,DOCID,CODE,CTN) values ('W1',7,'EME','CF');