For the schema (shown below, with primary keys indicated), write RA query for ea

Question

For the schema (shown below, with primary keys indicated), write RA query for each of the following. (State any reasonable assumptions if necessary.) You may write

a query in several steps.

Employee ( person_name, street, city)

Works(person_name, company_name, salary)

Company (company_name, city)

(a)Find the names of all employees in this database who do NOT livein the same city as the company for which they work. [Note: You should understand what “...the same city as the company for which they work” means.]

(b)Find the smallest total number of employees (of any company).

Explanation / Answer

1). person_name(employee ./ works ./ company)

ii. {p|e employee(c company(w works(w.company_name c.company_namep.person_name e.person_namee.person_name w.personname e.city c.city)))}

iii. {hperson_namei|company_name, salary(hperson_name, company_name, salaryi works(c, v(hcompany_name, ci company hperson_name, v, ci employee)))}

b) t1 company-nameGcount-distinct person-name (works)

t2 maxnum-employees(company-strength(company-name,num-employees)(t1))

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