Combining of 2 different tables in to a query/view

Question

Hi
I have 2 tables one is emp for employee details and another for courses for the courses which employee undergone.I want to create a view that contains the employees with each category went to the courses and rest of the employees didnt attended the courses in that group.The view or query should be combination of emp group wise by designation/groups who attended the courses and who didnt attended the courses.just an exmple of tables
Courses
emp emname job course
1 jon clerk msoffice
1 jon clerk office automation
2 rahul officer office automation
2 rahul officer spoken english
3 shyam officer spoken english
4 raj Manager office automation
Emp
empno ename job
1 jon clerk
5 ben clerk
2 rahul officer
3 shyam officer
6 rahim officer
4 raj manager
7 sandya manager
rgds
rateesh

Answer 1

Hi, Rateesh,
Sorry, I'm not sure I understand the problem. It would really help if you posted the results you want to get from the view.
Do you want to get all the information from the courses table, plus one row (from the emp table) for every employee who is not in the courses table?
The normal way to do that is an Outer Join.
For example, if you want to see all the departments (from the scott.emp table), and all of the employees in each department (from the scott.emp table), and you also want to see departments with no employees, you can say:
SELECT  d.deptno
,       e.ename
FROM             scott.dept  d
LEFT OUTER JOIN  scott.emp   e     ON d.deptno = e.deptho;Since your tables are denormaliized (that is, the empname and job are repeated in different tables), you can also do that with a UNION, like you tried. You'll get all of the data from the courses table (for the employees who are in the courses table), and the data from the emp table, but only for the employees who are not in the courses table. You can put a literal NULL in the course column of SELECT clause, since these people will have no course.
Using the scott.dept and emp tables, here's how to simulate an outer join with a UNION.
SELECT  deptno
,       emp
FROM    scott.emp
UNION
SELECT  deptno
,       NULL    AS emp
FROM    scott.dept     d
WHERE   NOT EXISTS (   -- Make sure this department is not in the emp table
                   SELECT  NULL
                   FROM    scott.emp
                   WHERE   deptno = d.deptno
                   );You should be able to use either of these techiques to get the view you want. Your emp table corresponds to scott's dept table, and your courses table corresponds to scott's emp table. That is, you can have 0 or more courses per emp, in much the same way that scott can have 0 or more emps per dept.