Queries Errors

Question

Hello,
i have abit of a problem with my queries
1) Sorting: Select all employees time.
SQL> select * from employees
2 group by employee_name;
select * from employees
ERROR at line 1:
ORA-00979: not a GROUP BY expression
This one I want to group
2) Grouping: List courses and group them by Course Level or Course Title
SQL> select course_id, course_title, course_level
2 from course
3 where course_level='L3'
4 group by course_title, course_level;
select course_id, course_title, course_level
ERROR at line 1:
ORA-00979: not a GROUP BY expression
Also this one I need to group
3) Comparison Operator (Not Equal): List all employees whose name is not Steve Smith.
This one I don’t know whats wrong as I want “not =” to “steve smith”
SQL> select employee_name
2 from employees
3 where employee_name != 'Steve Smith';
EMPLOYEE_NAME
STEVE SMITH
STEVE SMITH
STEVE SMITH
CHARLIE SPRING
CHARLIE SPRING
CHARLIE SPRING
ALI HUSSEIN
ALI HUSSEIN
ALI HUSSEIN
DANIEL WHITE
DANIEL WHITE
EMPLOYEE_NAME
DANIEL WHITE
PETER HAYDEN
PETER HAYDEN
PETER HAYDEN
15 rows selected.
Thank You in advance

Answer 1

user13038840 wrote:
Last 2 questions promise, Ive tried it and its giving me a headache. Ive done everything else so just need help on these 2.
SQL> select id, first_name
2 from trainer
3 where first_name IN (select first_name
4 from trainer
5 where course type = 'computer networks');
where course type = 'computer networks')
ERROR at line 5:
ORA-00920: invalid relational operator
2)
SQL> select count (*)
2 from employees
3 where employees is NULL;
where employees is NULL
ERROR at line 3:
ORA-00904: "EMPLOYEES": invalid identifier
Edited by: user13038840 on Apr 26, 2010 5:20 AMPerhaps you meant,( besides an extra coffee ;) ):
where course_type = 'computer networks');
(I added an underscore)
and 'employees' is your table name, not a column name.