SQL & PL/SQL :: Inner Join Used Using Clause?

Equi join (Inner join)

It is the simplest join or inner. An equijoin combines rows that have equivalent values for the specified columns.

SQL> select * from x;

NAME EMAIL EMPID
Sam email@removed 1060
Rose email@removed 1061

[code]....

don't consider above mentioned queries I got valuable outputs.

NAMEEMAIL EMPID NAME EMAIL EMPID
samemail@removed 1060 sam email@removed 1060
roseemail@removed 1061 rose email@removed 1061
sonaemail@removed 1062 sona email@removed 1062

Inner join shows matches only when they exist in both tables.so , i got records 1060,1061,1062

// Referencing columns used in a USING clause.
SQL> select x.name,x.email,x.empid from x
2 inner join y
3 using (empid);

select x.name,x.email,x.empid from x
*
ERROR at line 1:
ORA-25154: column part of USING clause cannot have qualifier

so query rewritten as

SQL> select x.name,x.email,empid from x
2 inner join y
3 using (empid);
NAME EMAIL EMPID
--------------- --------------- ----------
sam email@removed 1060
rose email@removed 1061
chris email@removed 1062

I mean see two different outputs.first output records twice displayed ... Yes i agree that is Inner join.second output records not displayed twice... common records only displayed once ,in x and y.

I think should n't use a table name or alias when referencing columns used in a USING clause... am i right ????

I want to know both are inner joins .how Oracle is determined both outputs ?