Ronan Lucio wrote:
Hi,
Supposing we have for tables: One master table (student) and three independent tables. There is no relationship between them. Each of the three table have a relationship with table student.
City | Teacher | TestLocal ==== | ======= | ========= city_id | teac_id | test_id city_name | teac_name | test_name
Student ======= stud_id stud_name city_id teac_id test_id
When the application shows the student screen, itīs need to make 4 SQL queries.
Is it wise to make only one query even donīt having any relations ship between the three ones?
SELECT city_name, teac_name, test_name
FROM City, Teacher, TestLocal
WHERE city_id = Student.city_id
AND teac_id = Student.teac_id
AND test_id = Student.test_id
AND Student.stud_id = $cod_student
SELECT city_name, teac_name, test_name FROM Student LEFT JOIN City ON Student.city_id=City.city_id LEFT JOIN Teacher ON Student.teac_id=Teacher.teac_id LEFT JOIN TestLocal ON Student.test_id=TestLocal.test_id WHERE Student.stud_id = $cod_student
Or is it better to make 3 distinct SELECT?
What should be better for the application and DB?
Thanks, Ronan
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