im doing this query on mysql, but its giving me duplicate results sets:
this is my query:
SELECT u.username, u.picture, m.id, m.user_note, m.reply_id, m.reply_name, m.dt, m.votes_up
FROM user u, notes m
WHERE m.topic_id =14
ORDER BY m.dt DESC
i dont understand why its doing it? please help :))
EDIT: table schema
notes{id, user_id, topic_id, user_note, reply_id, reply_name, votes_up, dt}
user {user_id, username, password, email, full_name, picture, date_join}
You have no join condition on your where clause. Its create a Cartesian product of your results I would guess.
So you have two tables when you select from two tables it gives you the Cartesian Product of the results sets or all the rows in A X all the rows in B. What you need to do is link the two tables together ie to relate them. select * from User as U,Notes as N where U.ID = N.UserID Then add your other constraints.
Related
I have two tables (users and posts) and I want to write out all posts (among other things) by one user. I'm thinking I should use a JOIN and WHERE but I get an error for using WHERE.
This is my code:
SELECT username, post, joinDate, title, info FROM users
WHERE userId='18'
JOIN posts ON users.userId=posts.userId
ORDER BY date DESC
I'm new to this and perhaps there is a better way but I can't figure it out atm.
Thankful for all answers!
The JOIN clause comes before the WHERE clause, after the FROM clause. First you join together all the tables you need, then you do your filtering with WHERE. Like this:
SELECT username, post, joinDate, title, info
FROM users
JOIN posts ON users.userId=posts.userId
WHERE users.userId='18'
ORDER BY date DESC
try like below
SELECT u.*,p.*
FROM users u JOIN posts p ON u.userId=p.userId
WHERE u.userId=18
ORDER BY date DESC
where will be after join and 18 is int datatype value so not need single quote for this and use alias for avoiding ambigous column name
SELECT username, post, joinDate, title, info
FROM users
JOIN posts ON users.userId=posts.userId and users.userId='18'
ORDER BY date DESC
if userId is in users table then YES you can use where userId='18'.
If userId is in posts table then it should be userId='18' be in join part.
Two tables: users and story
Want to select all from both tables, but need a different alias for users.id vs story.id
$sql = "select id as userid, name, status from users as t1, id as msgid, data, msg, xdir from story as t2 where...
Getting syntax error.
Any help?
You need to write a join. And you need to use table prefixes when referring to the column names that appear in both tables to distinguish them.
The entire SELECT list comes before the FROM and JOIN clauses.
SELECT u.id AS userid, name, status, s.id AS msgid, msg, xdir
FROM users AS u
JOIN story AS s ON s.authorid = u.id
WHERE ...
I am just tinkering with SQL as I am trying to get into more complex statements. I don't know this qualifies for it or not but please guide how to go about it.
I have looked at JOINS and some question of Multiple Select Statements but unable to understand them correctly.
I have the following two tables:
emp table:
emp_id, name, address, org_id
books table:
id, emp_id, status, org_id
where emp_id in books table is foreign key referencing emp table.
I need to fetch all the records from books table of a particular org. But along with that I need to get all the data of respective employee like name, address along the result.
Please guide me in the right direction.
Thanks
Try this
select B.*,E.name,E.address from books B
inner join employee E
on B.emp_id=E.emp_id
where B.org_id=1;
I took value of of org_id as 1 for test purpose.
SELECT books.id, books.emp_id, books.status, books.org_id, emp.name, emp.address
FROM books
JOIN emp ON emp.emp_id = books.emp_id
WHERE books.org_id = '3'
As the other said, the org_id from emp table makes no sense. You must remove it from the table.
if you want all records from the books table try this
Select b.id,c.emp_id,b.status,e.name,e.address
from emp_table e
Left join books_table b
on(e.emp_id=b.emp_id)
where e.org_id='3' and b.org_id='3'
You can use this query this will gives you all book record with particular org_id along with all employee record
SELECT * FROM emp as e1
LEFT JOIN books as b1 ON e1.emp_id = b1.emp_id WHERE e1.org_id = 'YOUR_ID'
UNION ALL
SELECT * FROM emp as e1
RIGHT JOIN books as b1 ON e1.emp_id = b1.emp_id WHERE e1.org_id = 'YOUR_ID'
The following query should work for you:
SELECT b.id, b.status, b.org_id, e.emp_id, e.name, e.address
FROM Books b LEFT JOIN Employee e
ON e.emp_id = b.emp_id
WHERE b.org_id = 100
This would be the query for org 100.
It appears that your current schema is not normalized very well:
Employee: emp_id, name, address, org_id
Books: id, emp_id, status, org_id
The two tables both store the org_id, which presumably means the same thing.
This query might give you the results you want. You might want to learn more about joins in SQL. A LEFT JOIN gives you all records from one table, and matching records from another.
SELECT books.*,
emp.name AS emp_name,
emp.address AS emp_address,
emp.org_id AS emp_org_id
FROM books
LEFT JOIN emp ON books.emp_id = emp.emp_id
WHERE books.org_id=?
you can use this for all recors both tables :
select * from books
inner join emp on
books.emp_id=emp.emp_id
where books.emp_id=emp.emp_id
Keeping this clean and to the point:
I have two MySQL tables, users (id, nick) and bans (id, banned, bannedBy, length).
I want to display in a table a list of bans, but instead of displaying the banned ID and the bannedBy ID, I want to display their nick.
I can use an JOIN to get the nick of one of them, in something like this:
SELECT bans.id,bans.banned,bans.bannedBy,bans.length,users.nick
FROM bans
JOIN users ON users.id=bans.banned
But then I can't get the bannedBy's nick, and vice verca.
I hope I was clear, thanks in advance for any help.
You have to join users table twice, on different keys.
SELECT
bans.id,
bans.banned,
bans.bannedBy,
bans.length,
u.nick as 'banedNick',
u2.nick as 'bannedByNick'
FROM
bans
JOIN
users u ON users.id = bans.banned
JOIN
users u2 ON users.id = bans.bannedBy
You can use two joins:
SELECT bans.id,bans.banned,b.nick as bannedBy,bans.length,u.nick
FROM bans
JOIN users u ON u.users.id=bans.banned
JOIN users b ON b.users.id=bans.bannedBy
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.