I have a table called website that contains some data about websites. The columns of this table are: id, website, quick_url, user_id, status, etc.
Each website that is in the table was added by a user, which is is saved in the user_id column.
I have another table called blocks that has only 3 columns: id, user_id, website_id.
I want to get all the websites from the website table, that were not added by a given user_id, but also, only the websites that were not blocked by the given user_id. So, websites that were not added by a given user or blocked by him.
Here is what I've tried:
SELECT * FROM website LEFT OUTER JOIN blocks ON tbl_website.userid = blocks.user_id WHERE website.user_id = blocks.user_id AND blocks.user_id = NULL AND website,user_id != '177' LIMIT 500;
It doesn't give me the wanted results ...
First, I've tried to do it like this:
SELECT * FROM tbl_website WHERE id<>(SELECT website_id from tbl_website_blocks WHERE user_id = '177')
which makes much more sense for me than my previous query, but I get this error: Subquery returns more than 1 row
I guess you can't have a "loop in loop" in an SQL query.
I'm aware that I could do two queries, and filter the results, but I would like to do it as much as possible from the SQL language, so that I don't "overload" the server.
Any suggestions would be appreciated.
In your second query rewrite the condition on
WHERE id not in (SELECT website_id from.....)
with <> you can compare it with just one value but your select returns list of values, so you can use not in to get results that are different then the selected list of IDs
Instead of '<>', try 'Not In'
SELECT * FROM tbl_website
WHERE id Not In (SELECT website_id from tbl_website_blocks WHERE user_id = '177')
I should also add this query is not a Join.
Related
I need help with this mysql query that executes too long or does not execute at all.
(What I am trying to do is a part of more complex problem, where I want to create PHP cron script that will execute few heavy queries and calculate data from the results returned and then use those data to store it in database for further more convenient use. Most likely I will make question here about that process.)
First lets try to solve one of the problems with these heavy queries.
Here is the thing:
I have table: users_bonitet. This table has fields: id, user_id, bonitet, tstamp.
First important note: when I say user, please understand that users are actually companies, not people. So user.id is id of some company, but for some other reasons table that I am using here is called "users".
Three key fields in users_bonitet table are: user_id ( referencing user.id), bonitet ( represents the strength of user, it can have 3 values, 1 - 2 - 3, where 3 is the best ), and tstamp ( stores the time of bonitet insert. Every time when bonitet value changes for some user, new row is inserted with tstamp of that insert and of course new bonitet value.). So basically some user can have bonitet of 1 indicating that he is in bad situation, but after some time it can change to 3 indicating that he is doing great, and time of that change is stored in tstamp.
Now, I will just list other tables that we need to use in query, and then I will explain why. Tables are: user, club, club_offer and club_territories.
Some users ( companies ) are members of a club. Member of the club can have some club offers ( he is representing his products to the people and other club members ) and he is operating on some territory.
What I need to do is to get bonitet value for every club offer ( made by some user who is member of a club ) but only for specific territory with id of 1100000; Since bonitet values are changing over time for each user, that means that I need to get the latest one only. So if some user have bonitet of 1 at 21.01.2012, but later at 26.05.2012 it has changed to 2, I need to get only 2, since that is the current value.
I made an SQL Fiddle with example db schema and query that I am using right now. On this small database, query is working what I want and it is fast, but on real database it is very slow, and sometimes do not execute at all.
See it here: http://sqlfiddle.com/#!9/b0d98/2
My question is: am I using wrong query to get all this data ? I am getting right result but maybe my query is bad and that is why it executes so slow ? How can I speed it up ? I have tried by putting indexes using phpmyadmin, but it didn't help very much.
Here is my query:
SELECT users_bonitet.user_id, users_bonitet.bonitet, users_bonitet.tstamp,
club_offer.id AS offerId, club_offer.rank
FROM users_bonitet
INNER JOIN (
SELECT max( tstamp ) AS lastDate, user_id
FROM users_bonitet
GROUP BY user_id
)lastDate ON users_bonitet.tstamp = lastDate.lastDate
AND users_bonitet.user_id = lastDate.user_id
JOIN users ON users_bonitet.user_id = users.id
JOIN club ON users.id = club.user_id
JOIN club_offer ON club.id = club_offer.club_id
JOIN club_territories ON club.id = club_territories.club_id
WHERE club_territories.territory_id = 1100000
So I am selecting bonitet values for all club offers made by users that are members of a club and operate on territory with an id of 1100000. Important thing is that I am selecting club_offer.id AS offerId, because I need to use that offerId in my application code so I can do some calculations based on bonitet values returned for each offer, and insert data that was calculated to the field "club_offer.rank" for each row with the id of offerId.
Your query looks fine. I suspect your query performance may be improved if you add a compound index to help the subquery that finds the latest entry from users_botinet for each user.
The subquery is:
SELECT max( tstamp ) AS lastDate, user_id
FROM users_bonitet
GROUP BY user_id
If you add (user_id, tstamp) as an index to this table, that subquery can be satisfied with a very efficient loose index scan.
ALTER TABLE users_bonitet ADD KEY maxfinder (user_id, tstamp);
Notice that if this users_botinet table had an autoincrementing id number in it, your subquery could be refactored to use that instead of tstamp. That would eliminate the possibility of duplicates and be even more efficient, because there's a unique id for joining. Like so.
FROM users_botinet
INNER JOIN (
SELECT MAX(id) AS id
FROM users_botinet
GROUP BY user_id
) ubmax ON users_botinet.id = ubmax.id
In this case your compound index would be (user_id, id.
Pro tip: Don't add lots of indexes unless you know you need them. It's a good idea to read up on how indexes can help you. For example. http://use-the-index-luke.com/
I have several tables in my database such as
comments
status
events
I’m trying to create an SQL query procedure which counts data from these different tables based on the userID entered and then sum up the counts to create a unique valued. This is what i’ve tried so far but i’m having problems with the syntax. Where am I going wrong??
SELECT COUNT(user_id) AS comments FROM comment
WHERE user_id= userID
UNION ALL
SELECT COUNT(creator_id) AS events FROM event
WHERE creator_id=userID;
In a union, the fields are combined based on order. So giving the count field a different name in each part of the union does not make two fields. It becomes the same field in the end. To differentiate which value came from which table, add a hardcoded string literal like so:
SELECT COUNT(user_id) AS rows, 'comment' as tablename FROM comment
WHERE user_id= userID
UNION ALL
SELECT COUNT(creator_id) AS rows, 'event' as tablename FROM event
WHERE creator_id=userID;
In database in table user I have three columns:
id
name
friends
In column friends are names of people who are friends with person whose name is stored in column name. Column friends looks like this:
friendname1,friendname2,friendname3,friendname4
Each of those friends have it's own row where name is equal to their name.
I also have another table called post where I have four columns:
id
name_posted
post
visible
What I would like now, is to select all posts from table post where name_posted is equal to name of the logged in user or any of his friends which are stored in column friends in table user.
Name of the logged in user is stored in variable $user.
For selecting only posts from logged in user I can use this:
$all_posts = mysqli_query($connect_db, "SELECT * FROM post WHERE name_posted='$user' AND visible='yes'");
but I don't know how to include to select also posts from his friends. Something like Facebook have, when you log in and you see your posts plus your friends posts. I don't know how they created that. Sorry for long post, I just wanted to give you detailed description.
For selecting data based on information across multiple tables I suggest reading up on MySQL Joins.
Maybe with two querys, first select friends something like this:
SELECT * FROM user WHERE name='$user'
You then have all his friends in string like this if I understood correctly :
friend1,friend2,friend3...
Explode $row['friends'] -> explode(',',$row['friends']); to get all friends names in array and then you can do another select in foreach loop to get all posts from friends and display it the way you like or you can even better do IN in query
select * from posts where name_posted IN ($row['friends'])
this is the other way, which would be longer
foreach($friendarray as $k=>$friend){
...
mysqli_query($connect_db,
"SELECT * from post where name_posted='$friend' AND visible='yes'");
...
}
and also the query you already have to get own posts. Don't forget to escape all values and stuff...
You could also join two tables but I cant write that query from my mind , would have to sit down and try it with real data but that would be ultimate solution for you.
Don't know if I hit it right but shout if you need help
You can do it in a single query with something like:
SELECT p.*
FROM user u
join post p
on (u.name = p.name or concat(',',u.friends,',') like concat('%,',p.name,',%')
AND p.visible='yes'
WHERE u.name='$user'
- but the performance is likely to be much poorer than if you had a properly normalised design for the relationship between users and their friends.
You should probably reconsider the design of your DB. From what you've described, you should have three tables: userinfo, friendship, posts.
That way, you can then do a quick union between all three tables to get what you're looking for in one query.
Let me talk about how I will solve that case if its required from me.
I will use the following tables
users - user_id, name, email and whatever I need
relations - relation_id, user_id, fiend_id -- this table will relate one user to other
posts - post_id, user_id, content, visible
Now basically we have everything needed.
For selecting all data from the currently logged user and all of his friend I will use the following query:
SELECT * FROM posts
WHERE Visible = 1
AND (
user_id IN (SELECT friend_id FROM relations WHERE user_id = 1)
OR
user_id = 1)
What I do here, I use nested queries to accomplish that.
The interesting part here is the nested query - which basically return "array" with the ids of my friends. MySQL IN function check the user_id against that "array" After that in the main parentheses I add OR user_id = 1 which is the my user_id.
In that way I should have the content which I want to use to my feed.
However this code I away from fast and optimized but it's good example how to do that.
Here is my php/MySQL task:
I have a table POSTS that contains num field that is the primary key and other information fields about the post (author, title, etc.). I also have a table LIKE that contains a userId field that is the primary key and a field POST that corresponds to the num field in posts. Given a specific userID, I need to get all of the rows from the POSTS table that the userId 'likes'.
Table 1 - posts
-num
-author
-title
Table 2 - likes
-userId
-postId
This is all in php so my first idea was to get all of the rows from the LIKES table where the userId matches the one given and store those rows in an array. Then I would iterate through the array and for each row I would search get the row of the POSTS table where postId=POSTS.num. However, this seems like it would be rather slow, especially since each iteration through the array would be a separate mysql query.
I am assuming there is a faster way. Would it be to use a temporary table or is there a better way to join the tables? I have to assume that both tables contain many rows. I am a mysql novice so if there is a better solution please explain why it is better. Thank you in advance for you help!
Try the following query:
SELECT
`posts`.*
FROM
`likes`
INNER JOIN
`posts` ON
`posts`.num = `likes`.postId
WHERE
`likes`.Userid = {insert user id here}
Depending on your schema (not sure if each record in 'likes' has to be unique, you may want to use the DISTINCT keyword on your select to filter out duplicates.
SELECT poli.* FROM (
SELECT po.* FROM posts po
JOIN likes li
ON li.postId = po.num
WHERE li.userId = '$yourGivenUserId'
) AS poli
$yourGivenUserId is the given userId.
With PHP I'm trying to run a SQL query and select normal columns as well as COUNT.
$sql_str = "select COUNT(DISTINCT name), id, adress from users";
$src = mysql_query($sql_str);
while( $dsatz = mysql_fetch_assoc($src) ){
echo $dsatz['name'] . "<br>";
}
The problem is that when I have "COUNT(DISTINCT name)," in my query, it will only return the first entry. When I remove it, it will return all matching entries from the db.
I could separate it and do 2 queries, but I'm trying to avoid this due to performance concerns.
What do I make wrong?
thx, Mexx
The ability to mix normal columns and aggregate functions is a (mis)feature of MySQL.
You can even read why it's so dangerous on MySQL's documentation:
https://dev.mysql.com/doc/refman/5.6/en/group-by-extensions.html
But if you really want to mix normal rows and a summary in a single query, you can always use the UNION statement:
SELECT COUNT(DISTINCT name), null, null FROM users GROUP BY name --summary row
UNION
SELECT name, id, address FROM users --normal rows
COUNT() is an aggregate function, it aggregates against the results of the rest of your query. If you want to count all distinct names, and not just the distinct names associated with the id and address that you are selecting, then yes, you will have to run two queries. That's just how SQL works.
Note that you should also have a group by clause when aggregating. I think the fact that MySQL doesn't require it is horrible, and it encourages really bad habits.
From what I understand, you want to get :
one line per user, to get each name/id/address
one line for several users at the same time, to get the number of users who have the same name.
This is not quite possible, I'd say.
A solution would be, like you said, two queries...
... Or, in your case, you could do the count on the PHP side, I suppose.
ie, not count in the query, but use an additionnal loop in your PHP code.
When you have a count() as part of the field list you should group the rest of the fields. In your case that would be
select count(distinct name), id, adress from users group by id, adress
select count(distinct name), id, adress
from users
group by id, adress
I'm assuming you want to get all your users and the total count in the same query.
Try
select name, id, address, count(id) as total_number
from users
group by name, id, address;