define the table map for all selected parameters as well

in ur case,

SQL> select First_Name, Last_Name, Address, a.User_Name, Status, University
from User_Info a, Admission_Code b, Univ_Code c, User_Admission_Status
d where a.User_Name=d.User_Name and b.Code=d.Admission_Code and
c.Code=d.Univ_Code;
select First_Name, Last_Name, Address,
User_Name, Status, University from User_Info a, Admission_Code b,
Univ_Code c, User_Admission_Status d where a.User_Name=d.User_Name and
b.Code=d.Admission_Code and c.Code=d.Univ_Code

the error u got is becoz of there are columns in ur table that are present in both mapped tables

i dint go thru all columns but i think User_Admission_Status and User_Info have same named column, User_Name, thus the error.

best wud b to use tablename.columnName format

like

SELECT
table1.column1, table2.column1, table2.column3
FROM
tblFirst table1,
tblSecond table2

even better would be using Joins instead of commas.

i hope it helps

Alias issue. Make sure to use alias for each column name in the select list.

select a.First_Name, a.Last_Name, a.Address, a.User_Name, c,Status, b.University from User_Info a, Admission_Code b, Univ_Code c, User_Admission_Status d where a.User_Name=d.User_Name and b.Code=d.Admission_Code and c.Code=d.Univ_Code;

I didn't try this but the logic sound right this way

Try This one

Here this is what I have created and this should yield the right result

 

SQL> desc User_Info
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 FIRST_NAME                                NOT NULL VARCHAR2(30)
 LAST_NAME                                 NOT NULL VARCHAR2(30)
 ADDRESS                                   NOT NULL VARCHAR2(100)
 USER_NAME                                 NOT NULL VARCHAR2(20)
 PASSWORD                                  NOT NULL VARCHAR2(20)

SQL> desc Admission_Code
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 CODE                                      NOT NULL NUMBER(38)
 STATUS                                    NOT NULL VARCHAR2(20)

SQL> desc Univ_Code
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 CODE                                      NOT NULL NUMBER(38)
 UNIVERSITY                                NOT NULL VARCHAR2(30)

SQL> desc User_Admission_Status
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 USER_NAME                                 NOT NULL VARCHAR2(20)
 UNIV_CODE                                          NUMBER(38)
 ADMISSION_CODE                                     NUMBER(38)

SQL> select a.First_Name, a.Last_Name, a.Address, a.User_Name, b.Status, c.University from User_Info a, Admission_Code b, Univ_Code c, User_Admission_Status d where a.User_Name=d.User_Name and b.Code=d.Admission_Code and c.Code=d.Univ_Code;

no rows selected

Good Luck