how to sort the contents of CLOB field - sql

Question

I have a table and some fields are CLOB type and the content in the CLOB was delimited by some separator such as '|' and usually the content in the filed looks like this : name2|name1|name3..., actually the length of the content is more than 40000 characters, so is there any way to sort the content by asc? I want to look the content like this: name1|name2|name3...
can any body help me?

Answer 1

If it's even remotely possible, I'd strongly suggest you change your data model - add a details table for the names. This will solve you a lot of pain in the future.
Anyhow, if you absolutely need to store a pipe-separated list of names in your CLOB field, I'd suggest this approach:
break the CLOB into separate rows (using a pipelined function)
sort the rows
aggregate the rows into a new CLOB
A (somewhat naive and untested) implementation of this approach:
create type stringtabletype as table of varchar2(4000);
create or replace function split_CLOB(p_Value in CLOB,
p_Separator in varchar2 default '|')
return stringtabletype
pipelined as
l_Offset number default 1;
l_Str varchar2(4000);
idx number;
begin
idx := dbms_lob.instr(lob_loc => p_Value,
pattern => p_Separator,
offset => l_Offset);
dbms_output.put_line(idx);
while (idx > 0)
loop
l_Str := dbms_lob.substr(p_Value,
idx - l_Offset,
l_Offset);
pipe row(l_Str);
l_Offset := idx+1;
idx := dbms_lob.instr(p_Value,
p_Separator,
l_Offset);
dbms_output.put_line(idx);
end loop;
-- pipe remainder of string
l_Str := dbms_lob.substr(p_Value,
dbms_lob.getlength(p_Value) - l_Offset + 1,
l_Offset);
pipe row(l_str);
return;
end;
create or replace function sort_stringtabletype(p_Values in stringtabletype)
return stringtabletype as
l_Result stringtabletype;
begin
select column_value bulk collect
into l_Result
from table(p_Values)
order by column_value;
return l_Result;
end;
create or replace function stringtabletype_to_CLOB(p_Values in stringtabletype,
p_Separator in varchar2 default '|')
return CLOB as
l_Result CLOB;
begin
dbms_lob.createtemporary(l_Result, false);
for i in 1 .. p_Values.count - 1
loop
dbms_lob.writeappend(l_Result,
length(p_Values(i)),
p_Values(i));
dbms_lob.writeappend(l_Result,
length(p_Separator),
p_Separator);
end loop;
dbms_lob.writeappend(l_Result,
length(p_Values(p_Values.count)),
p_Values(p_Values.count));
return l_Result;
end;
Example usage:
select stringtabletype_to_CLOB (
sort_stringtabletype(
split_CLOB('def|abc|ghic', '|')
)
) from dual
You could then use an UPDATE statement like
update my_table
set clob_field = stringtabletype_to_CLOB (
sort_stringtabletype(
split_CLOB(my_table, '|')
)