具有两个联接和简单逻辑的sql查询

Question

Please find the fiddle http://sqlfiddle.com/#!9/4a4aff/7

Friends_list Table

 | id | user_id | Friend_id | status
 |  1 |   1     |    24     |   P
 |  2 |   18    |    26     |   P

User Table

| ID | email   | password  |  ..N
 |  1 |   xx    |    xx     |   xx
 |  2 |   xx    |    xx     |   xx

from those both table i want to get all the users listed without the users whose status was P or B in friends list table it seems to be simple using joins but in wordpress this code is not working and the query is as below.

select DISTINCT u.ID, u.user_nicename from wp_users u
LEFT JOIN friends_list f ON f.friend_id=u.ID
WHERE f.status  NOT IN ('P', 'B')

Answer 1

You must join tables with user id like below:

LEFT JOIN friends_list f ON f.user_id =u.ID

select DISTINCT u.ID, u.user_nicename from wp_users u
    LEFT JOIN friends_list f ON f.user_id=u.ID
    WHERE f.status  NOT IN ('P', 'B')

Add two records at friends_list table with Q and Z status for testing

INSERT INTO `friends_list` (`id`, `user_id`, `Friend_id`, `status`) VALUES
(80, 1, 26, 'P'),
(79, 18, 26, 'P'),
(78, 1, 24, 'P'),
(79, 20, 24, 'Q'),
(80, 21, 24, 'Z');

sqlfiddle working example

Answer 2

From what I understand you want ALL user except the those who has P or B as status. To get those users that don't have a value in the friends_list table at all you can add a null check to your query.

select DISTINCT u.ID, u.user_nicename from wp_users u
LEFT JOIN friends_list f ON f.friend_id=u.ID
WHERE f.status NOT IN ('P', 'B') OR f.status IS NULL

I'm also unsure if you're joining on the right column? Should it be user_id instead of friend_id?

Answer 3

Just change the binding column like this :-

select DISTINCT u.ID, u.user_nicename from wp_users u
LEFT JOIN friends_list f ON f.user_id=u.ID
WHERE f.status NOT IN ('P', 'B');

Answer 4

Change your query as below. If you only want data from first table then no need join query only use inner query

select DISTINCT u.ID, u.user_nicename from wp_users u WHERE u.ID not in 
(select f.friend_id from friends_list f where f.status IN ('P', 'B')) order by u.ID;

Fiddle

EDIT

select DISTINCT u.ID, u.user_nicename from wp_users u
LEFT JOIN friends_list f ON f.friend_id=u.ID
WHERE f.status NOT IN ('P', 'B') OR f.status IS NULL ORDER BY u.ID

Answer 5

You can use this query, your fiddle is showing blank result as you have only data with P Status, try to add one more entry with some other status then you will get the result.

select DISTINCT u.ID, u.user_nicename from wp_users u left join friends_list f 
on f.friend_id=u.ID where f.status is NULL