SQL Developer bind variables prompt: force string values - sql

Question

I'm trying to use SQL Developer bind variables prompt to speed up query execution, but I'm not getting the desired output: looks like the values I put in get converted in number.
Table description:
Nome Null Type
------------------ -------- ------------
NUM NOT NULL VARCHAR2(13)
IS_OK NUMBER(1)
initial situation:
select NUM, IS_OK from numbers_table where NUM = cast(:dn as varchar2(13));
NUM |IS_OK |
------------|------|
08331930078 |1 |
working updates:
1.
update numbers_table set IS_OK = 0 where NUM = 08331930078;
update numbers_table set IS_OK = 0 where NUM = '08331930078';
ouput:
'1 row updated'
non-working updates:
1.
update numbers_table set IS_OK = 0 where NUM = :dn;
update numbers_table set IS_OK = 0 where NUM = cast(:dn as varchar2(13));
output:
'0 rows updated'
Don't know what else can I do to force the value being parsed as a string.
SQL Developer version 4.1.3.20

Answer 1

That's interesting, and looks like a bug. You don't actually need to cast, the value from the 'enter binds' window is a string anyway, so this works:
update numbers_table set IS_OK = 0 where NUM = :dn;
when the zero-padded string 08331930078 is entered in the dialog.
The cast is not needed but ought to still work. If you run as a script instead, with a defined bind variable, then both forms do work:
var dn varchar2(13);
exec :dn := '08331930078';
update numbers_table set IS_OK = 0 where NUM = :dn;
rollback;
update numbers_table set IS_OK = 0 where NUM = cast(:dn as varchar2(13));
rollback;
You get 1 row updated for both statements. Going back to running as a statement still prompts and still has the same (odd) behaviour even when the bind variable has been defined in a script in the same session.
Incidentally, when you do:
update numbers_table set IS_OK = 0 where NUM = 08331930078;
what you're actually doing, as you can see form the execution plan's predicate section, is:
update numbers_table set IS_OK = 0 where to_number(NUM) = 8331930078;
which will stop any index on the num column being used, and may result in unexpected results - in this case, if these are e.g. UK phone numbers you probably won't have the same value with and without the leading zero, but it's something to be wary of generally.