What's the reason behind adding ':'|| and ||':' to items in INSTR function?

Question

Hi,
I noticed in examples that when the INSTR function is used items and the search strings are preceeded/followed by ':'|| and ||':' and I was just wondering why this is so. Does this not just add a : to the start and finish of the item and string? Is there an advantage over just coding it like so:
instr(upper(OBJECT_ID), upper(:P18_OBJECT_ID)) > 0)
rather than
instr(':'||:P18_STATUS||':',':'||STATUS||':') > 0
Cheers,
simon.

Answer 1

Simon,
I don't know about the instr vs. like question. For the other question, I've seen this used mostly for checking for the presence of a token within a colon-delimited string of values. Consider:
******** Right Answer ********
SQL> select 1 from dual where instr(':'||'CREATE:UPDATE:DELETE:'||':', ':'||'CREATE'||':') > 0;
1
1
******** Wrong Answer ********
SQL> select 1 from dual where instr('CREATE:UPDATE:DELETE:', ':'||'CREATE'||':') > 0;
no rows selected
******** Right Answer ********
SQL> select 1 from dual where instr(':'||'CREATE:UPDATE:APPLY_CHANGES:DELETE:'||':', ':'||'APPLY'||':') > 0;
no rows selected
******** Wrong Answer ********
SQL> select 1 from dual where instr(':'||'CREATE:UPDATE:APPLY_CHANGES:DELETE:'||':', 'APPLY') > 0;
1
1
Scott