Joining trois tables en utilisant MySQL

Question

j'ai trois tables nommées

**Student Table** 
------------- 
id name 
------------- 
1  ali 
2  ahmed 
3  john 
4  king 

**Course Table** 
------------- 
id name 
------------- 
1  physic 
2  maths 
3  computer 
4  chemistry 

**Bridge** 
------------- 
sid cid 
------------- 
1  1 
1  2 
1  3 
1  4 
2  1 
2  2 
3  3 
3  4 
4  1 
4  2 

Maintenant, pour afficher le nom de l'étudiant avec le nom du cours qu'il avait étudié comme,

**Result** 
--------------------------- 
Student  Course 
--------------------------- 
ahmed   physic 
ahmed   maths 
ahmed   computer 
ahmed   chemistry 
ali   physic 
ali   maths 
john   computer 
john   chemistry 
king   physic 
king   maths 

Je construis requête suivante

select s.name as Student, c.name as Course from student s, course c join bridge b on c.id = b.cid order by s.name 

Mais il ne retourne pas le résultat requis ...

Et ce serait pour la forme normalisée, si je veux trouver qui est responsable sur les autres:

**employee** 
------------------- 
id  name 
------------------- 
1   ali 
2   king 
3   mak 
4   sam 
5   jon 

**manage** 
-------------- 
mid  eid 
-------------- 
1   2 
1   3 
3   4 
4   5 

et veut obtenir ce résultat:

**result** 
-------------------- 
Manager  Staff 
-------------------- 
ali   king 
ali   mak 
mak   sam 
sam   jon 

Answer 1

Utilisez simplement:

select s.name "Student", c.name "Course" 
from student s, bridge b, course c 
where b.sid = s.sid and b.cid = c.cid 

Answer 2

syntaxe Utilisez ANSI et il sera beaucoup plus clairement la façon dont vous joindrez les tables:

SELECT s.name as Student, c.name as Course 
FROM student s 
    INNER JOIN bridge b ON s.id = b.sid 
    INNER JOIN course c ON b.cid = c.id 
ORDER BY s.name 

Answer 3

formulaire de Normaliser

select e1.name as 'Manager', e2.name as 'Staff' 
from employee e1 
left join manage m on m.mid = e1.id 
left join employee e2 on m.eid = e2.id 

Answer 4

Utilisez ceci:

SELECT s.name AS Student, c.name AS Course 
FROM student s 
    LEFT JOIN (bridge b CROSS JOIN course c) 
    ON (s.id = b.sid AND b.cid = c.id); 

Answer 5

SELECT * 
FROM user u 
JOIN user_clockits uc ON u.user_id=uc.user_id 
JOIN clockits cl ON cl.clockits_id=uc.clockits_id 
WHERE user_id = 158 

Answer 6

SELECT 
employees.id, 
CONCAT(employees.f_name," ",employees.l_name) AS 'Full Name', genders.gender_name AS 'Sex', 
depts.dept_name AS 'Team Name', 
pay_grades.pay_grade_name AS 'Band', 
designations.designation_name AS 'Role' 
FROM employees 
LEFT JOIN genders ON employees.gender_id = genders.id 
LEFT JOIN depts ON employees.dept_id = depts.id 
LEFT JOIN pay_grades ON employees.pay_grade_id = pay_grades.id 
LEFT JOIN designations ON employees.designation_id = designations.id 
ORDER BY employees.id; 

Vous pouvez joindre plusieurs tables comme cet exemple ci-dessus.

Answer 7

requête pour joindre plus de deux tables:

SELECT ops.field_id, ops.option_id, ops.label 
FROM engine4_user_fields_maps AS map 
JOIN engine4_user_fields_meta AS meta ON map.`child_id` = meta.field_id 
JOIN engine4_user_fields_options AS ops ON map.child_id = ops.field_id 
WHERE map.option_id =39 AND meta.type LIKE 'outcomeresult' LIMIT 0 , 30 

Answer 8

   select tb1.knames, 
       tb3.*, 
       tb2.* 
       from tb3 join tb1 
       on tb3.nid=tb1.nid 
       join tb2 on 
       tb3.id=tb2.id