oracle之''空子符串與NULL是否相等

SQL> create table t_nbr(a number);
 
Table created
 
SQL> insert into t_nbr values(1);
 
1 row inserted
 
SQL> insert into t_nbr values('');
 
1 row inserted
 
SQL> commit;
 
Commit complete
 
SQL> commit;
 
Commit complete
 
SQL> select * from t_nbr;
 
         A
----------
         1
 
SQL> select a,dump(a) from t_nbr;
 
         A DUMP(A)
---------- --------------------------------------------------------------------------------
         1 Typ=2 Len=2: 193,2
           NULL
 
SQL>

 

小結:

         1,''和NULL在oracle儲存皆視為NULL