I've imported by phpbb3 forum in bbpress using the built-in importer. All of the anonymous users from bbpress who didn't have accounts, but were allowed to post are disconnected from there posts and everything is showing up as anonymous in bbpress. I grabbed all the post_usernames from phpbb_posts and created users with this query:
INSERT INTO wp_users (user_login)
SELECT DISTINCT post_username
FROM phpbb_posts
Now I'm trying to do a query between the 3 different tables. Something along these lines:
SELECT ID FROM wp_users
INSERT INTO wp_posts(post_author)
WHERE wp_posts(post_date) = phpbb_posts(post_time)
AND phpbb_posts(post_username) = wp_users(user_login)
Obviously this isn't right... probably syntax errors, but I also need to add some way of telling MySQL that the user_login has to be attached to the ID from the first line. Hopefully this makes sense. Thanks in advance for any help!
Updated queries:
SELECT ID FROM wp_users
SELECT post_time FROM phpbb_posts = post_date
SELECT post_username FROM phpbb_posts = user_login
hopefully this syntax makes more sense. These did work and they select the right information. The problem is I don't know how to write the WHERE statement properly and like you said baskint, I think I need to make the last statement a sub-query somehow. Thanks again!
I am still not sure what are the PK's (Primary Key) and FK's (Foreign Key) relationships of each table. However, assuming that wp_users is the primary table and phpbb_posts.post_username is the FK of wp_users.user_login...:
SELECT `wp_users`.`ID`
FROM `wp_users` INNER JOIN
(SELECT `phpbb_posts`.`post_username` FROM `phpbb_posts`, `wp_posts` WHERE `phpbb_posts`.`post_time` = `wp_posts`.`post_date` ) AS `posts`
ON `wp_users`.`user_login` = `posts`.`post_username`;
EDIT (Dec-05-2012):
After chatting and going through specific, #sbroways had to change data-types on some fields and a few other modifications. In turn, the final query turned out to be:
SELECT wp_users.*, ws_posts.*
FROM wp_users INNER JOIN ws_posts
ON wp_users.user_login = ws_posts.user_login
you're right. your syntax is confusing and not correct. trying to understand what you are trying to accomplish. in second query, why are you selecting and inserting at the same time? perhaps i am missing something, but can you state what you are trying to pull out from which tables and how you would like to see the results in plain English?
Also you can think in terms of sub-queries (SELECT * FROM b WHERE id IS IN (SELECT Id from a). You can cascade this a few times and perhaps get to your answer.
Related
I am assigning unique users to vouchers on my website.1 user may have more than one voucher assigned to them but cannot be assigned the same voucher twice.I have 2 mysql tables that I am fetching data from.
tbl_users
tbl_voucher_users
When a user click on a button on my website, they pass along a voucher_id with which I use to display eligible users that can be assigned this voucher ( I.e Users that have not been assigned to this voucher ).
Below is how I am getting the users where voucher_id = 8
$user_data = DB::table('users')
->leftJoin('voucher_users', 'users.id', '=', 'voucher_users.user_id')
->where('voucher_users.voucher_id','!=',8) //User not assigned this voucher
->select('users.*','users.id as userID','voucher_users.*')
->get();
My problem
I am able to left join without the where clause and get results from both Users table and Voucher_users table having eliminated all users assigned voucher_id=8.
However, the results also include users who are assigned other vouchers but also the voucher I am assigning.
i.e
Expected resulsts would be users: 8,11,12,13,14 having eliminated users: 1,4
But my current results are:4,8,11,12,13,14
How do I get rid of the user 4 to prevent double assignment?
Thanks to the suggestion above by #Kevin Lynch to use NOT EXIST .. I simplified the code to:
SELECT users.*
FROM
users
WHERE
NOT EXISTS(SELECT user_id FROM voucher_users WHERE voucher_users.user_id = users.id AND voucher_id=9)
It works so far, I can then covert it to Laravel style
NOT EXISTS would be a good solution if this were to remain a small project (or if you could put more constraints on the users to keep the dataset small perhaps by limiting based on user created date or similar).
However if you can't do such a thing, this query will eventually give you problems because under the hood, mysql will be running that sub-query for each record returned in the main query. You can check https://dev.mysql.com/doc/refman/5.6/en/subquery-materialization.html for more information.
A different solution which would handle the scaling quite a bit better would be to generate a temporary table of users that have the voucher you are looking to remove...
create temporary table tmp_voucher_user (user_id int not null, primary key (user_id)) as
select distinct user_id from voucher_users where voucher_id = 8;
Now that we have a table of users we which to remove, all we need to do is worry about a simple left join...
select users.*, user_voucher.*
from users
inner join user_voucher on users.id = user_voucher.user_id
left join tmp_voucher_user on users.id = tmp_voucher_user.user_id
where tmp_voucher_user.user_id is null -- this part is important, it's only going to grab users where there isn't a match on tmp_user_voucher
Unfortunately this isn't as clean as just doing a NOT EXISTS and I don't believe Laravel supports a way to build temporary tables outside of just writing a raw query but it should scale quite a bit better.
I am trying to find out how to find the emails that do not exist in a table using the emails from the conditional.
I could create a table with these emails but that seems like overkill for what I need it for.
What I am looking for is a query that would show me the conditional value and NULL as the user ID.
Is this possible?
I have a query like this:
SELECT u.uid, u.mail
FROM `users` u
WHERE u.mail IN (
'alot#of',
'emails#that',
'ineed#tofind',
)
This works great at finding the emails and associating the user id. Now I need to identify which emails do not exist in the result. I am currently only using 56 emails and 6 do not appear in the list. I am trying to identify which emails are not found.
NOT IN won't work as I have over 40,000 users. I only want to identify the emails not found from my conditional. I have 56 emails and only 50 results. I need to identify the 6 not found (they may not even be in the table at all)
Let me attempt to clarify this a little more:
I am given a list of emails for supposed accounts in the system. I am trying to find the accounts from the given email. This part is fine. Now, the issue I am having, I was given 56 emails but only 50 were found. I need to identify which emails out of the 56 were not found. The emails are all thrown into the conditional. NOT IN won't work because it would return all user but the 50 that were found. (roughly 40,000) I just need to identify the emails from the conditional that were not found in the table.
Thanks for any insight or suggestions to do what I need.
There isn't a way to do what you want without creating some additional items to track the emails. Basically, you're trying to get MySQL to tell you which items in the WHERE portion aren't found, but MySQL can only tell you about rows in a table.
You need to make a secondary table that stores the email addresses from your list, call it list. I would make it a single column table with just the emails. Then LEFT JOIN it against the users table and find where the uid is null.
SELECT u.uid, l.mail
FROM `list` l
LEFT JOIN `users` u ON u.mail=l.mail
WHERE u.uid IS NULL
As posted in the comments, NOT IN may be helpful. But there are also other ways. One of them is to left join your table with the result of your query and show only non-coincident rows:
select u.uid, u.mail
from users as u
left join (
select u.uid, u.mail
from users
where mail in ('alot#of','emails#that','ineed#tofind')
) as a on u.uid = a.uid
where a.uid is null;
Add the fields you need to the join (if uid is not enough)
So your question now becomes more complicated... you want to find all the E-Mails in your condition that are not found in your table.
As far as I know, there's not a simple SQL sentence that will give you that... but you can work with temp tables and get it. The solution implies:
Create a temporary table to hold the values you want to search (and add the appropriate indexes to it)
Insert the values you want to search
Execute a select query to find non-matching rows
So... let's do it:
-- 1. Create a temp table to hold the values
drop table if exists temp_search_values;
create temporary table temp_search_values (
mail varchar(100),
unique index idx_mail(mail) -- Don't allow duplicate values here
);
-- 2. Insert the search values
insert into temp_search_values (mail) values
('alot#of'),('emails#that'),('ineed#tofind');
-- 3. Execute the query
select a.*
from users as u
left join temp_search_values as a on u.mail = a.mail
where u.mail is null;
Remember: Temporary tables are only visible to the connection that created them, and are deleted when the connection is closed or killed.
NULL is a strange result. It's not true and it's not false. If you want to check for it, you have to look specifically.
SELECT u.uid, u.mail
FROM `users` u
WHERE u.mail NOT IN (
'alot#of',
'emails#that',
'ineed#tofind',
) and u.uid IS NULL
* Oh, I see what you're getting at. This will work, although it's not pretty. *
select * from
(SELECT 'emails#that' as v
UNION SELECT 'alot#of' as v,
UNION SELECT 'ineed#tofind' as v
) as test
left join users on u.mail = test.v
where u.uid is null
I have three different tables - subscribers, unsubscribers, mass subscribers.
I'd like to print out each email from the mass subscribers table. However that email can only be printed if it doesn't exist in both subscribers and unsubscribers tables.
I know how to do this with arrays, however I want a plain mysql query.
What would mysql query be?
Thanks!
You can do that with a subquery (this is slow! Please read below the line):
SELECT email
FROM subscribers
WHERE email NOT IN(SELECT email FROM unsubscribers)
However, this is very bad for performance. I suggest you change the way you have your database, with just 1 table subscribers, and add a column active(tinyint). When someone unsubscribes, you set that value from 1 to 0. After that you can stay in 1 table:
SELECT email FROM subscribers WHERE active=1
This is faster because of some reasons:
No subquery
The where is bad, because you are going to select a heap of data, and compare strings
Selecting on integer in VERY fast (especially when you index it)
Apart from the fact that this is faster, it would be better for your database structure. You dont want two tables doing almost the same, with emailadresses. This will create duplicate data and a chance for misalignments
You sound like someone who doesn't have much experience with SQL. Your title does point in the right direction. Here is how you put the components together:
select m.*
from mass_subscribers m
where not exists (select 1 from subscribers s where s.email = m.email) and
not exists (select 1 from unsubscribers u where u.email = m.email);
NOT EXISTS happens to be a very good choice for this type of query; it is typically pretty efficient in both MySQL and other databases.
Without subqueries, using join
SELECT mass_subscribers.*
FROM mass_subscribers ms
LEFT JOIN subscribers s ON ms.email=s.email
LEFT JOIN unsubscribers us ON us.email=s.email
WHERE
ms.email IS NULL
AND
us.email IS NULL
A small question may be it is silly but I am not getting idea how to solve this problem
select * from customers where id in(select assigned from users where username='test');
in the above query
select assigned from users where username='test'
this returns 1,2
but the condition where in doesnot work which should be like below
select * from customers where id in(1,2);
this is not the exact output i am just guessing that it might be this way. which is not so the problem is occuring.
i am getting only one row that is corresponding to 1
so help me figuring this out.
please check the sqlfiddle below:
http://sqlfiddle.com/#!2/95c28/2
thanks
SELECT DISTINCT c.*
FROM customers c
JOIN users u ON FIND_IN_SET(c.id, u.assigned) IS NOT NULL
Putting comma-separated values is a bad idea in relational databases, it makes everything more complicated. You should use a relation table instead, so you can write a normal equality join. The above query cannot be indexed, so it will be very innefficient if the tables are large.
SQLFIDDLE
if select assigned from users where username='test' returns 1,2. This means your customer table contains only Id=1.
I want to copy an existing MySQL table over to a duplicate table, but with two additional fields populated by data retrieved from other queries. It's for a forums software that never captured the original creation date of the thread (it always overwrote the time with the most recent reply).
So I want to take the existing table, 'threads'
thread_id
thread_author
thread_subject
thread_last_reply_date
and create a new table, 'new_threads' of the same structure, but with two extra fields:
thread_id
thread_author
thread_subject
thread_last_reply_date
thread_creation_date
thread_last_poster_id
Both thread_last_reply_date and thread_last_poster_id could be populated from dependent queries.. For example, last_poster_id with a query of:
SELECT post_author FROM posts WHERE thread_id = ? AND post_date = thread_last_reply_date
And for the thread_creation_date:
SELECT MIN(post_date) FROM posts WHERE thread_id = ?
That's essentially the process I would do with a PHP script.. A series of SELECTs and then inserting records one by one. Any advice or direction on how to do this type of process in pure SQL would be crazy helpful (if it's possible).
EDIT: an example of the technique would be helpful. I don't need an exact answer for the above. I'm sure everyone has better things to do.
Just had a similar problem.
This solution worked for me:
INSERT INTO `new_thread` SELECT *,null,null FROM `thread` WHERE 1=1
To create your target table (empty):
CREATE TABLE new_threads
SELECT t.*, thread_creation_date date, thread_last_poster_id number
FROM thread where 1=0;
and to populate it:
insert into new_threads(thread_id, thread_author, thread_subject, thread_last_reply_date, thread_creation_date, thread_last_poster_id)
(select t.*,
min(p.post_date),
(SELECT p1.post_author
FROM posts p1
WHERE p1.thread_id = t.thread_id
AND p1.post_date = t.thread_last_reply_date) thread_last_poster_id
from threads t, posts p
where t.thread_id = p.thread_id;
(untested)