I believe there is a good way to do. I searched and tried but could not find.
I want to join three tables like this (or a better way, please suggest)
SELECT listing.*, users.username, review.rNumber
FROM listing, users,review
WHERE users.uid=listing.cuid and listing.lid=review.lID
But I don't want the review.rNumber I want to get sum of it like sum(rNumber). Because one listing can have many reviews.. Thank you..
Here is what I want to achieve with this query
All the values from listing table.
only username from users table
sum of reviews from review table
The relation is
users.uid=listing.cuid and listing.lid=review.lID
or
users.uid=listing.cuid=review.sellerID
Please let me know if I need to add table..
Thanks :)
you can get the sum for user with proper group by but for join with all the listing result you could use a dinamic join
SELECT listing.*, t.username, t.sum_rNumber
fFROM listing
INNER JOIN users ON users.uid=listing.cuid
INNER JOIN review ON listing.lid=review.lID
INNER JOIN (
SELECT users.username as username, sum( review.rNumber) sum_rNumber
FROM listing
INNER JOIN users ON users.uid=listing.cuid
INNER JOIN review ON listing.lid=review.lID
GROUP BY users.username
) t on users.username = t.username
(and is more readable the explicit join sintax)
Related
I have two tables in database, named users(store user details) and posts(store post details). Now i want to get data from both tables. Like user_image from users and post description from post.
I am using this query
SELECT * FROM `users`AS u,`posts` WHERE u.user_id IN (SELECT user_id FROM `posts`)
But it returns duplicate data. I have 2 users and 3 posts but it returns 6 posts.
Try something like:
Select a.user_image, b.post_description from users as a join posts as b on a.user_id = b.user_id
Do an inner join & you shall get the desired result
In the above query a & b are alias for the two different tables. I you do not want to use alias you can also write it as users.user_image in your select statement.
Write the fields you want from both the tables in your select statements.
The below image will help you understand the inner join
Inner Join Circle for understanding
Use group by as below:
SELECT * FROM `users`AS u,`posts` WHERE u.user_id IN (SELECT user_id FROM `posts`) group by u.user_id
What about
Select * FROM user u right join posts p on u.id = p.user_id
?
if you want to get data from both tables you need to use joins.and you make sure the two tables are interlinked by primary keys
so use this can help
select user_image,post_description from users join posts on users.user_id=posts.user_id;
I have written a query using inner join which consist of multiple tables
SELECT *
FROM admin_info
INNER JOIN admin_login
INNER JOIN gender
INNER JOIN admin_type
INNER JOIN area
INNER JOIN document_type
INNER JOIN permissions
ON admin_login.admin_id=admin_info.admin_id
AND admin_type.admin_type_id=admin_info.admin_type_id
AND area.area_id=admin_info.area_id
AND document_type.document_id=admin_info.document_id
AND permissions.permission_id=admin_info.permission_id
The above query works but gives multiple results of the same record or duplicate records
Please help me fix the query or provide with an alternative to this query
also please suggest me ways to optimize the query for faster processing??
The above Query
SELECT *
FROM admin_info
INNER JOIN admin_login
INNER JOIN gender
INNER JOIN admin_type
INNER JOIN area
INNER JOIN document_type
INNER JOIN permissions
ON admin_login.admin_id=admin_info.admin_id
AND admin_type.admin_type_id=admin_info.admin_type_id
AND area.area_id=admin_info.area_id
AND document_type.document_id=admin_info.document_id
AND permissions.permission_id=admin_info.permission_id
Below Given is the screen shot of the results.
I want only one record per person and not duplicate records?
Apart from that when i use foreach/while loop the results vary please help?
Actually The problem was with gender table which had no reference in the query as soon as i removed the gender table inner join it worked as expected!
I have two tables: 'posts' and 'users' every post has a 'ref_id' column to get the user id who posted it.
Now, I am getting posts this way:
$this->db->query("SELECT * FROM posts WHERE time > '$timeLimit' LIMIT 50");
I can't understand how to join every result to get the poster related data as well. What I am doing right now is basically a loop inside a loop, where foreach of the result, get their user info. But it is pretty obvious that this is very wrong,
Apparently I need to start using joins, but how does one do it? this should be a really simple example to work with, I suppose.
Any help? Thank you.
SELECT posts.*, users.*
FROM posts
INNER JOIN users
ON posts.posted_by = users.id;
Like this:
SELECT
posts.*,,
users.Username
FROM posts
INNER JOIN users ON posts.ref_id = users.user_id;
Explanation:
To JOIN to any tables with each others, there are two things; the JOIN type and the join condition. There are three main types of join:
INNER JOIN, only the rows that match the join condition will be returned from the two tables no more rows. But:
LEFT OUTER JOIN, when you join two tables you will have one on the left of the join keyword and the other one will be in the right:
FROM Table1 <------------- This is the left table.
LEFT OUTER JOIN table2 .... <------------- This is the right table.
In LEFT OUTER JOIN the unmatched rows from the left table will be included in the result set.
RIGHT OUTER JOIN the unmatched rows from the right table will be included in the result set.
CROSS JOIN this will perform a Cartesian product from the two tables.
In our query, the query will reutrn all the users from the users table only if the ref_id equal to the user_id column form the posts table.
For more information and explanations:
A Visual Explanation of SQL Joins.
Another Visual Representation of SQL Joins.
Join syntax in MySQL
SELECT user.name
FROM users
INNER JOIN posts
ON posts.ref_id == user.id
AND posts.time > 50
http://www.w3schools.com/sql/sql_join_inner.asp
I need a little help setting up my query. I'm simply trying to access the amount of people who are in the same 'clan' by joining these two tables together, clan, users. Each users has a column 'clan' which is the same as the table clan's column 'roomOwner' and then I'm trying to get the table clan's information along with the amount of members so it would be like: room, roomOwner, members
So basically all I have is this:
SELECT c.*, count(u.clan) AS members FROM clans c inner join users u WHERE c.roomOwner = u.clan ORDER BY members;
It only shows one clan though. Any help please?
Your query has no GROUP BY clause. and I think it's only returning single record right? LEFT JOIN is needed here since there are possibilities that a clan has no member.
SELECT b.roomOwner, COUNT(a.clan) memberCount
FROM clan b
LEFT JOIN users a
ON a.clan = b.roomOwner
GROUP BY b.roomOwner
ORDER BY memberCount
You forgot GROUP BY. Do you have some "id" column in "clans" table? Group by that "id"
SELECT c.*, count(u.clan) AS members
FROM clans c
inner join users u ON c.roomOwner = u.clan
GROUP BY clans.id
And you need LEFT JOIN there instead of INNER JOIN if you want to see info about all clans, even having 0 users.
Perhaps this will help:
select c.*, count(links.id) as members
from clans c
left join users u on c.roomOwner = u,clan
group by u.clan
order by members
So, I understand how the relationships work in mysql but I'm having a hard time figuring out how its implemented in my code.
For example, say I have the 3 tables.
Table 1: users - user id, username, user city
Table 2: categories - category id, category name
Table 3: user_categories - user id, category id
If I were to query the database for every user that was in a particular city and list them out with the all of the categories they belong to... How would I do this? Would I need to loop through the results and do a separate query for each user, then list the results? Or, is there some magic query that will return a multidimensional array?
I believe the above would be many-to-many, correct me if I'm wrong....
EDIT In the user_categories table, a user can contain more than 1 category, I'm trying to figure out how to return all of them
Thanks!
You're absolutely right, it is a many-to-many query.
And from what I understand, what you're looking for is the ability to have some kind of hierarchical result to display, meaning for one user, have an array of all the categories he's assigned to...
Couple of things you could do:
Option 1: Query the users table:
SELECT u.user_id, u.username, u.user_city WHERE city = 'somecity';
From the results, get all the user_id's that match, put them in an array.
array(1,3,4,5)
Then execute a query by joining the 2 tables categories and user_categories, and passing the array as a comma separated list in a where in:
SELECT user_categories.user_id, categories.category_name
FROM user_categories INNER JOIN categories ON user_categories.category_id = categories.category_id
WHERE user_categories.user_id IN (1,3,4,5)
This will give you a list of user-id, category name that you can use in your script with the previous results to build your result set
option 2: my preferred, use MySQL's GROUP_CONCAT(http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat).
SELECT users.user_id, users.user_name, GROUP_CONCAT(categories.category_name) AS categories
FROM users
INNER JOIN user_categories ON users.id = users_categories.user_id
INNER JOIN categories ON user_categories.category_id = category.id
WHERE user.user_city = 'somecity'
GROUP BY user.user_id
This will return something like:
user_id username categories
1 u1 cat1, cat2, cat3
2 u2 cat1, cat3
You can specify the separator by using SEPARATOR in group_concat.
You need to JOIN the tables.
If I were to query the database for every user that was in a particular city and list them out with the all of the categories they belong to
SELECT *
FROM users
INNER JOIN user_categories
ON (user_id)
INNER JOIN categories
ON (category_id)
WHERE ...
You could try:
SELECT u.user_id, u.username, u.user_city, c.category_id, c.category_name
FROM users u
INNER JOIN user_categories uc ON u.user_id = uc.user_id
INNER JOIN categories c ON uc.category_id = c.category_id
WHERE u.user_city = 'Cityname';
I haven't tested this, and there might be a more efficient way to do it, but it should work.
If you are unfamiliar with joins in mysql, check this out.