how can i join 3 tables in mysql php - php

Question

I have 3 tables tags,tag_type,user_alert
table structure is as follows:
CREATE TABLE `tags` (
`tag_id` int(11) NOT NULL,
`tag_name` varchar(255) CHARACTER SET utf8 NOT NULL,
`tagtype_id` int(11) NOT NULL,
`status` tinyint(1) NOT NULL,
`is_deleted` tinyint(1) NOT NULL,
`created_at` datetime NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=6 ;
CREATE TABLE IF NOT EXISTS `tag_types` (
`tagtype_id` int(11) NOT NULL,
`tagtype_name_en` varchar(100) CHARACTER SET utf8 NOT NULL,
`tagtype_name_fr` varchar(100) NOT NULL,
`display_order` int(11) NOT NULL,
`tag_color` varchar(50) CHARACTER SET utf8 NOT NULL,
`status` tinyint(1) NOT NULL DEFAULT '1',
`is_deleted` tinyint(1) NOT NULL DEFAULT '0',
`created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00'
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=11 ;
CREATE TABLE IF NOT EXISTS `user_alert` (
`user_alert_id` int(11) NOT NULL,
`tag_id` int(11) NOT NULL,
`user_id` int(11) NOT NULL,
`is_removed` enum('yes','no') DEFAULT 'no',
`created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=6 ;
I have created query, but it is not working for me.
select t.tag_name,t.tag_id,ty.tag_color,ty.tagtype_name_en as tagtype_name from tags as t INNER JOIN tag_types as ty ON t.tagtype_id=ty.tagtype_id INNER JOIN user_alert as ua ON ua.tag_id != t.tag_id where t.tagtype_id='5' and ua.user_id != '14'
I want to make query such that
I am passing tagtype_id and user_id
when I pass tagtype_id I can get all tag which belongs to that tagtyped_id and don not want to select tags in which user has subscribed.
but I am not able to do it.I know the answer will be simple but don't know how to do it.can anybody please help me?

Answer 1

In JOIN, you must use "=" and dont use "!=".
your condition must apply in where statement NOT in join.

Answer 2

Maybe this is what you are looking for (untested as i don't have this DB)
select t.tag_name,
t.tag_id,
ty.tag_color,
ty.tagtype_name_en as tagtype_name
from tags as t
INNER JOIN user_alert as ua
ON ua.tag_id <> t.tag_id
INNER JOIN tag_types as ty
ON ua.tag_id = ty.tagtype_id
where t.tagtype_id = '5'
and ua.user_id <> '14

Answer 3

Assuming the Table definition you supplied here is accurate; the problem is that you don't have a tagtype_name_en Field in your "tag_types" table and you are trying to access it while it doesn't exist.
// YOUR TABLE DEFINITION/COLUMNS:::
TABLE 1 - tags:
tag_id
tag_name
tagtype_id
TABLE 2 - tag_types
tagtype_id
tag_color
tagtype_name_en
TABLE 3 - user_alert
tag_id
user_id
UPDATE: ADDED GROUP BY CLAUSE
$sql = "SELECT
t.tag_name, t.tag_id,
ty.tag_color,ty.tagtype_name_en AS tagtype_name
FROM tags AS t
LEFT JOIN tag_types AS ty ON t.tagtype_id=ty.tagtype_id
LEFT JOIN user_alert AS ua ON ua.tag_id!=t.tag_id
GROUP BY t.tag_id
WHERE t.tagtype_id='5' AND ua.user_id != '14'";

Answer 4

Why dont you try with this <> not equal to operator instead of !=
SELECT * FROM `tags` AS `t` INNER JOIN `tag_types` AS `ty` ON t.tagtype_id = ty.tagtype_id INNER JOIN `user_alert` AS `ua` ON ua.tag_id <> t.tag_id WHERE t.tagtype_id = '5' AND ua.user_id <> '14'
UPDATED
Try this "LEFT JOIN"
SELECT * FROM `tags` AS `t` INNER JOIN `tag_types` AS `ty` ON t.tagtype_id = ty.tagtype_id LEFT JOIN `user_alert` AS `ua` ON ua.tag_id = t.tag_id WHERE t.tagtype_id = '5' AND ua.user_id <> '14' AND ua.tag_id IS NULL