nptel assingnment sql

Question

Comments

Answer is a) but there is misprint in resulting relation, item_name of 3 and 7 not matching.

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from this question, we have to note down that

comp_id of food table doesn't referencing comp_id of company table. (i.e., comp_id of food table is not a foreign key)

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@Shaik why?

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@srestha

mam, 20 is not in comp_id in company table but it is present in food table

Answer 1

in both relation comp_id is common attribute se we can take natural join but we have to check  left outer join and right outer join .in company relation the element of attribute comp_id is (15,16,17,18,19) and in food relation the element of comp_id is (15,16,17,18,19,20) for left outer join all the element of comp_id  of first relation will be present and there will be matching with the other joined relation if it does not match then null will be assign.so according to this option (A) is correct but there is miss print for item no. 3 and 7 which is already commented.