Update a subst() with other substr() value from same row

Question

Oracle 10.2.4.0
Given table MYTEST:
Name                                      Null?    Type
NAME_IND                                           VARCHAR2(15)
LOCAL_DATA                                         VARCHAR2(30)need to update every row, effectivley doing something like this:
update mytest
set substr(local_data,1,4) = substr(local_data,27,30)Obviously that code doesn't actually work, but at least implies what I need to do, and am having a hard time getting my head wrapped around exactly how to make it happen.
Expected input would be like:
NAME_IND        LOCAL_DATA                    
bert            12345678901234567890123456AAAA
bigbird         12345678901234567890123456BBBB
ernie           12345678901234567890123456CCCC and expected result would be
NAME_IND        LOCAL_DATA                    
bert            AAAA5678901234567890123456AAAA
bigbird         BBBB5678901234567890123456BBBB
ernie           CCCC5678901234567890123456CCCC

Answer 1

Frank Kulash wrote:
Hi,
In the SET clause of an UPDATE statement, the items to the left of the = signs must be columns in your table.
If you want to change local_data, in whole, or in part, then you say
SET  local_data = ...Now, what is the value to which you want to set it? If I understand correctly, it's the concatenation of two things
(1) The 4 characters starting a position 27 of the original local_data, and
(2) the part of the original local_data starting at position 5
The way to code that is
UPDATE  mytest
SET     local_data = SUBSTR (local_data, 27, 4)
            || SUBSTR (local_data, 5)Remember, the 3rd argument to SUBSTR is the length of the substring you want to extract, not the ending position.Right. Actually I had thought of that, but for some reason was thinking there would need to be a subselect, or even possibly an anonymous block of PL/SQL to get the value of the substr()'s for the 'current' row. After posting, shutting down, and heading home, my head cleared a bit and so was all set to give it a try, and it was exactly what I needed. Thanks for the lead.