The sql below doesn't return any row:

select a.PHONE,a.content from tb1 a,tb2 b where a.phone=b.phone;

But tb1 and tb2 has the same PHONE structure and many PHONE data are
same.


tb1 structure:
...
phone varchar(18) nullable
...

tb2 structure:
...
phone varchar(18) nullable
...

Thank you.