SqlDeveloper Issue -

Question

Hi Masters!
I have an issue, with the sqldeveloper, there is a filter that sends some different values using a field that is varchar2, which is being selected as follows:
Select *
from postcode_lookup
where postcode = '3034';
And it is sending some data from the database, but when you use 5030 without single quotes sometimes sends something and other times sends nothing.
If it is a varchar why you can use the filter without single quotes.
I need to know what is happening with the data, the filter, the sqldeveloper, and the database Oracle 10g.
I will be grateful if you can give me a clue.
Paola.
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Answer 1

Hi,
>>I need to know what is happening with the data, the filter, the sqldeveloper, and the database Oracle 10g.
I'm not a "Master", but ... Regardless the use of Oracle SQL Developer, in fact, Oracle will make a implicit conversion and if there is an index on this column, then the optimizer will not use it. In addition, you can have some problems if you insert "numeric characters" and "Alpha characters" together in this table. Take a look at below:
LEGATTI@ORACLE10> create table x (cod varchar2(10));
Table created.
LEGATTI@ORACLE10> insert into x values (1);
1 row created.
LEGATTI@ORACLE10> insert into x values (10);
1 row created.
LEGATTI@ORACLE10> insert into x values (200);
1 row created.
-- The row is returned without problem
LEGATTI@ORACLE10> select * from x where cod=10;
COD
10
LEGATTI@ORACLE10> insert into x values ('A');
1 row created.
-- Now, you have a problem
LEGATTI@ORACLE10> select * from x where cod=10;
ERROR:
ORA-01722: invalid number
no rows selected
-- In this case, you are obligated to use single quotes
LEGATTI@ORACLE10> select * from x where cod='10';
COD
10
LEGATTI@ORACLE10> delete from x where cod='A';
1 row deleted.
-- About the index, that I mentioned, take a look at below
LEGATTI@ORACLE10> create index i_cod on x (cod);
Index created.
LEGATTI@ORACLE10> SET LINESIZE 130
LEGATTI@ORACLE10> SET PAGESIZE 0
-- Without single quotes you can see that index was not used because the Oracle made an implicit conversion, therefore it was performed a FTSLEGATTI@ORACLE10> explain plan for select * from x where cod=10;
Explained.
LEGATTI@ORACLE10> select * from table(dbms_xplan.display);
Plan hash value: 3276047201
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |      |     1 |     7 |     3   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS FULL| X    |     1 |     7 |     3   (0)| 00:00:01 |
Predicate Information (identified by operation id):
1 - filter(TO_NUMBER("COD")=10)
Note
   - dynamic sampling used for this statement
17 rows selected.
-- Now, using single quotes you can see that index was used to make a range scan instead a FTS
LEGATTI@ORACLE10> explain plan for select * from x where cod='10';
Explained.
LEGATTI@ORACLE10> select * from table(dbms_xplan.display);
Plan hash value: 3592172846
| Id  | Operation        | Name  | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT |       |     1 |     7 |     1   (0)| 00:00:01 |
|*  1 |  INDEX RANGE SCAN| I_COD |     1 |     7 |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
1 - access("COD"='10')
Note
   - dynamic sampling used for this statement
17 rows selected.Cheers
Legatti