adding the result of count in Oracle Sql

Question

I'm trying to the number of the elements of two tables here is what I've tried :

 select 
((select count(*) from Person,Professor where ID_Person = ID_Professor)  + 
(select count(*) from Person, Student where ID_Person = ID_Student ))

well this doesn't work any Idea how can I do this? thanks in advance

score 1 · Accepted Answer · 2013-06-17 22:46:19Z

1

You're just missing a from dual on the end, to make the outer select a complete statement.

Exactly as you had it plus from dual:

select 
((select count(*) from Person,Professor where ID_Person = ID_Professor)  + 
(select count(*) from Person, Student where ID_Person = ID_Student ))
from dual

edited Jun 17, 2013 at 22:46

answered Jun 17, 2013 at 22:37

user2404501

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1 Comment

Engine Over a year ago

thanks for your answer, but honestly I don't get what do you mean ?

pratik garg · Accepted Answer · 2013-06-17 22:45:26Z

1

Wumpus Q. Wumbley has given correct suggestion for Oracle database.

For your question you can try following query as well -

   select sum(c_total) 
    from (
      select (select count(*) from professor 
               where professor.id_professor=person.id_person)
           + (select count(*) from student 
               where student.id_student=person.id_person) c_total
      from person
     group by person.id_person)

answered Jun 17, 2013 at 22:45

pratik garg

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