How do relational algebra with double join?

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I have this query:

select DE.nombre as departamento, count(H.sex) as nroHijos_Varones from hijos H 
    inner join empleado E on H.id_padre = E.id
    inner join dept DE on E.dept = DE.cod
    where H.sex = 'M' group by DE.nombre;

What I have tried:

I'm not sure if the part with inner join is fine:

E <- empleado
DE <- dept
H <- hijos

 T1 <- H ⨝_H.id=padre E ⨝_DE.cod = E.dept H

Posted 20-May-20 15:16pm

shirleyliz

Updated 20-May-20 21:50pm

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Maciej Los 21-May-20 3:50am

How could we know that?
Note, that we don't see your screen and we can't read in your mind.

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Maciej Los · Answer 1 · 2020-05-20T21:51:00

Please, read my comment to the question first...

If you would like to know how many people with specific gender is employed in departments, use this:

SQL

select DE.nombre as departamento, H.sex, count(H.sex) as nroHijos_Varones
from hijos H 
    inner join empleado E on H.id_padre = E.id
    inner join dept DE on E.dept = DE.cod
where H.sex = 'M'
group by DE.nombre, H.sex;