Question

Having trouble writing two mysql queries for this schema

The low level conceptual model of the restaurant database is provided below:

DATABASE:

RESTAURANT (res_name[pk], City, Phone, Owner_SSN[pk,fk])

FOOD (food_name[pk], Type, Country, Proof)

CUSTOMER (SSN[pk], Name, Birth_year, Fav_food[fk], Gender)

LIKES (SSN[pk,fk], food[pk,fk]) SERVES (res[fk], foods[fk])

OWNER (SSN[pk], Name, City, Address, Phone)

QUERIES

14) Find the total number of foods that are liked by customers. Note that if a food is repeatedly liked by several people, it is just counted as once.

15) List the number of old customers from each gender, only if they are more than 1. For instance, if the number of old male customers is 1, it should not be shown in the results. A customer is considered old if he/she is at least 65 years old.

Answer 1

Select COUNT(DISTINCT l.food) FROM FOOD f Inner join LIKES l ON f.food_name=l.food;

Above mentioned query has two level of function used to get results.

Select Gender,count(SSN) AS Count customers from CUSTOMER WHERE (YEAR(CURDATE()) - birth_year) >=65 GROUP BY GENDER HAVING Count(SSN)>1;