PostgreSQL connecting two tables with 2 common attributes on Query - sql

Question

I have 2 entities; castfilm and staff in my erd that have a common attribute employeeid. Now, I wanted to Query in postgre to show the attributes that are related to the specific person that has an employeeid no. 307 where his fname and lname is David and Kaye respectively.
My erd looks like this: enter image description here
The attributes that I wanted to show are fname, lname, castrole, filmtitle, filmgenre, filmyear, companyname, staffposition, artistname and soundtitle that are related to the film of the employee named David Kaye
Here's my query:
SELECT distinct fname,lname,castrole, filmtitle, filmgenre, filmyear, companyname
FROM employee,
castfilm,
film,
production,
company
WHERE employee.employeeid = 307
AND employee.employeeid = castfilm.employeeid
AND castfilm.filmid = film.filmid
AND production.companyid = company.companyid
AND production.filmid = film.filmid
[output][2]
How do I show the other staffs and casts that are related to the specific movie that David Kaye is on?

Answer 1

You can use EXISTSstatement:
The argument of EXISTS is an arbitrary SELECT statement, or subquery.
The subquery is evaluated to determine whether it returns any rows. If
it returns at least one row, the result of EXISTS is "true"; if the
subquery returns no rows, the result of EXISTS is "false".
In the subquery you should check if for given filmid there exists an employeeid in castfilm. And this employeeid should be 307.
Like this:
SELECT distinct fname,lname,castrole, filmtitle, filmgenre, filmyear, companyname
FROM employee,
castfilm,
film,
production,
company
WHERE employee.employeeid = castfilm.employeeid
AND castfilm.filmid = film.filmid
AND production.companyid = company.companyid
AND production.filmid = film.filmid
AND EXISTS (
SELECT
employeeid
FROM
castfilm
WHERE
filmid = film.filmid AND
employeeid = 307
);
Please, note that film.filmid is used in the subquery.
Furthermore, as #jarlh noted, you could use JOIN syntax, like this:
SELECT
fname,
lname,
castrole,
filmtitle,
filmgenre,
filmyear,
companyname
FROM
employee
JOIN castfilm
ON (employee.employeeid = castfilm.employeeid)
JOIN film
ON (castfilm.filmid = film.filmid)
JOIN production
ON (film.filmid = production.filmid)
JOIN company
ON (production.companyid = company.companyid)
WHERE
EXISTS (
SELECT
employeeid
FROM
castfilm
WHERE
filmid = film.filmid AND
employeeid = 307
);