Oracle is not null cannot filter null values

Experts ,

I have a strange problem today , Our simple query statement , Added is not null The filter conditions of , But in the query results , Some of the values of this field , No matter how you look at it, it is empty . By analyzing these outliers utl_raw.cast_to_raw transformation , perhaps dump From the result of function conversion , No matter how you look at them, they are null . See the screenshot for details . Have experts ever encountered such a situation .oracle 11204 edition ,oracle linux System .

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Take the answer 1：

select * from tb where field=chr(0);

oracle There is a problem , Reference resources ：
https://www.modb.pro/db/33720

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Other answers 1：

select * from tb where field=chr(0);

oracle There is a problem , Reference resources ：
https://www.modb.pro/db/33720

Other answers 2：

Field ='' or Field is not null

Other answers 3：

The fields are empty and null It's different , You can press this : Field !='' or Field is not null Remove as a condition

Other answers 4：

Guess the value in your field is not NULL, It's Spaces .
For example, the test is as follows ：

SQL> create table test_null(id number,c1 varchar2(16));Table created.SQL> insert into test_null values(1,NULL);1 row created.SQL> insert into test_null values(2,'');-- No spaces 1 row created.SQL> insert into test_null values(3,' ');-- Yes 1 A space 1 row created.SQL> commit;Commit complete.SQL> select id,dump(c1,1016) res,length(c1) from test_null;        ID RES                                                          LENGTH(C1)---------- ------------------------------------------------------------ ----------         1 NULL         2 NULL         3 Typ=1 Len=1 CharacterSet=AL32UTF8: 20                                 1SQL> 

Other answers 5：

Check the length , Check it out ascii code ( It may be invisible characters )：

select length(c_customer_accounts),ascii(c_customer_accounts) from dual;

Other answers 6：

dump once , Look at what's inside , contrast ASCII Just look at the code watch and you'll know what it is ！

select c_customer_accounts,dump(c_customer_accounts)  from your_table ....

Other answers 7：

It may be a carriage return

Other answers 8：

Problem closed : The problem has been solved