I want to show post from users that specified user is followed and i have two tables at below. but its query is very slow.
table user
id | username
1 | name1
2 | name2
3 | name3
..
..
table post
id | poster_id | post_content
1 | 2
2 | 3
3 | 10
..
..
table follow
followerid | followtoid
1 | 2
1 | 3
2 | 10
..
..
Assume that all tables have more than 1000 rows.
This's SQL
SELECT *
FROM post
WHERE poster_id IN (
SELECT followtoid
WHERE followerid = $_SESSION['userid']
)
And this's the second cast is very slow too.
I want to list all member by order from their total posts.
SELECT *
FROM user
ORDER BY (
SELECT COUNT(id)
FROM post
WHERE post_id = user.id
) DESC;
Try indexing post.userid, post.poster_id, followtoid.followerid and user.user_id, using CREATE INDEX, and use LEFT JOIN clause on your queries instead:
SELECT *
FROM user u
LEFT JOIN SELECT poster_id, COUNT(*) as count FROM post p GROUP BY poster_id
ON (u.user_id = p.poster_id)
ORDER BY count DESC;
and:
SELECT * FROM post AS p
LEFT JOIN (SELECT followerid FROM followtoid) AS f
ON (p.userid=f.followerid)
WHERE p.userid = {$_SESSION['userid']}
Use a JOIN for the first query
SELECT p.*
FROM post p
JOIN follow f ON p.post_id = f.followtoid
WHERE f.followerid = $_SESSION['userid']
and a JOIN plus a GROUP BY for the second
SELECT u.*, tbl.postCount
FROM user u
JOIN (
SELECT poster_id, COUNT(*) AS postCount
FROM post p
GROUP BY posterID
) tbl ON tbl.poster_id = u.id
ORDER BY postCount DESC
You can accomplish the second query without a subquery:
SELECT u.*, COUNT(p.poster_id) as postCount
FROM user u
LEFT JOIN post p
ON (u.user_id = p.poster_id)
GROUP BY u.user_id
ORDER BY postCount DESC;
Related
I have table 1: users
id | name |
1 | john |
2 | garry|
3 | sam |
And table two called posts:
id | user_id | title | posted
1 | 1 | Something | 1551128761
2 | 1 | Else | 1551128761
3 | 3 | Some Title | 1551122745
4 | 2 | Demo Title | 1551129777
5 | 3 | Something | 1551126793
user_id in the second table is the id of the user in the first table
I need to get the latest post out of the table and i'm doing that currently by using this query:
SELECT u.id, u.name, p.title
FROM users AS u
LEFT JOIN posts AS p
ON p.user_id= u.id
WHERE p.posted = ( SELECT MAX(posted) FROM posts WHERE user_id = u.id )
ORDER BY u.id
LIMIT 15
But the problem with this query is that if the timestamp is the same for the same user (in this example for user with user_id 1 the timestamp is the same) i'm getting both of those rows instead of just the latest one(the latest one has the highest id)
Try this MySQL query:
SELECT u.id,
u.name,
p.title
FROM users AS u
JOIN posts AS p
ON p.id = (SELECT pi.id
FROM posts AS pi
WHERE pi.user_id = u.id
ORDER BY pi.id DESC
LIMIT 1);
Tested and works fine. Here is a demo: DBFiddle
To speed up select query, consider adding indexes
ALTER TABLE posts ADD INDEX(user_id);
ALTER TABLE posts ADD INDEX(posted);
One option using id column from posts table as following. This is assuming id is going to be different for each post record is posts table. Demo here
SELECT u.id, u.name, p.title,p.posted
FROM users AS u
LEFT JOIN posts AS p
ON p.user_id= u.id
WHERE (p.posted,p.id) = ( SELECT MAX(posted),MAX(id) FROM posts WHERE user_id = u.id )
ORDER BY u.id
How about restructuring the query slightly?
SELECT posts.title, users.id, users.name
FROM posts, users
WHERE posts.user_id = users.id
ORDER BY posts.posted DESC, posts.id DESC
LIMIT 1
Essentially selecting from posts, ordering by the posted timestamp and secondly the id of the post in descending order in case timestamp is the same.
I have three table content information about posts
and each table has Post_id it's foreign_key for Post table
first table = `likes`
second table = `Comment`
and last one = `Visitor`
each Table has some info about users like session or id and etc
i need to create new view table contain post id and the number of visitor , likes , comment
i tried this
SELECT *
from (
select id , count(id) as Comment
from Post left join Comment on id = Post_id
group by id
UNION
select id, count(id) as Visitor
from Post left join Visitor on id = Post_id
group by id
UNION
select id, count(id) as Likes
from Post left join Likes on id = Post_id
group by id
) CountsTable
GROUP BY CountsTable.id
but it didnt work .
i dont know why the result is only the first inner select
in my example the result is
| id | Comment|
|--------|------- |
| 1 | 55 |
| 2 | 25 |
| 3 | 12 |
i expect something like that
| id | Comment | Likes | Visitor |
|--------------|-------|---------|
| 1 | 55 | 100 | 2000 |
No need to use UNION. Count the records for each post in all three tables and Left Join result with Post table
Try something like this
SELECT id,
comments,
vistors,
likes
FROM Post p
LEFT JOIN (SELECT Count(Post_id) comments, Post_id
FROM Comment
GROUP BY Post_id) c
ON p.id = c.Post_id
LEFT JOIN (SELECT Count(Post_id) vistors, Post_id
FROM Visitor
GROUP BY Post_id) v
ON p.id = v.Post_id
LEFT JOIN (SELECT Count(Post_id) likes, Post_id
FROM Likes
GROUP BY Post_id) l
ON p.id = l.Post_id
You can do it with a Left Join query, e.g.:
select u.id, count(distinct l.id) as likes, count(distinct c.id) as comments
from user u left join likes l on u.id = l.user_id
left join comments c on u.id = c.user_id
group by u.id;
Here is SQL Fiddle.
SELECT id, SUM(Comment),SUM(Visitor),SUM(Likes) from (
select id , count(id) as Comment, 0 as Visitor, 0 as Likes
from Post left join Comment on id = Post_id
group by id
UNION ALL
select id, 0 as Comment, count(id) as Visitor , 0 as Likes
from Post left join Visitor on id = Post_id
group by id
UNION ALL
select id, 0 as Comment, 0 as Visitor, count(id) as Likes
from Post left join Likes on id = Post_id
group by id
) CountsTable
GROUP BY CountsTable.id
I'm trying to show post by order them with sum of comment and like.
There are three table using in this query post,comment and like
for table like it has column type that keep value like or unlike.
SQL
SELECT (SELECT COUNT(id) AS count_comment
FROM comment WHERE comment.post_id = post.post_id),
(SELECT COUNT(id) AS count_like
FROM like WHERE like.post_id = post.post_id AND like.type = 'like'),
(SELECT COUNT(id) AS count_unlike
FROM like WHERE like.post_id = post.post_id AND like.type = 'unlike'),
post.* FROM post
ORDER BY (count_comment + count_like - count_unlike) DESC;
So, this is an example when it shows on the page
post_id | comment | like | unlike | (comment+like-unlike)
4 | 5 | 3 | 1 | 7
1 | 2 | 3 | 0 | 5
2 | 1 | 1 | 4 | -2
... | ... | ... | ... | ...
My problem is my SQL is very slow, please suggest another way if it can. I've tried to use JOIN but i can't figured out how its SQL should be, please help thanks.
Using a derived table for each of the counts, the query below counts comments, likes, unlikes for each post and then joins the counts to the post table by post_id.
SELECT
p.post_id,
COALESCE(c.comment_count,0) comment_count,
COALESCE(l.like_count,0) like_count,
COALESCE(ul.unlike_count,0) unlike_count,
(COALESCE(c.comment_count,0)
+ COALESCE(l.like_count,0)
- COALESCE(ul.unlike_count,0)) total
FROM post p
LEFT JOIN (
SELECT c.post_id,
COUNT(*) comment_count
FROM comment c
GROUP BY c.post_id
) c ON c.post_id = p.post_id
LEFT JOIN (
SELECT l.post_id,
COUNT(*) like_count
FROM like l
WHERE l.type = 'like'
GROUP BY l.post_id
) l ON l.post_id = p.post_id
LEFT JOIN (
SELECT ul.post_id,
COUNT(*) unlike_count
FROM like ul
WHERE ul.type = 'unlike'
GROUP BY ul.post_id
) ul ON ul.post_id = p.post_id
ORDER BY total DESC
There where 2 mysql tables users(id,name,city) and friend_list(id,userid,friend,status).
Now i need to get three random friends from the friend_list table and their name from users table.
Friend_list table
id | userid |friend |status
1 | 1 | 2 | friends
2 | 3 | 1 | friends
3 | 2 | 3 | friends
users table:
id | name
1 | xxx
2 | yyy
3 | zzz
I need query something like this.
SELECT f.*,u.name FROM friend_list f,users u WHERE (f.userid = 1 or f.friend = 1) AND f.status = 'friends' AND f.userid = u.id AND f.order by RAND() limit 3
but for eg: it should select 1 in userid column and also from friend column.
I m trying to achieve it without using JOIN's
You can use the oreder by rand() as in below query.
select Friend_list.friend,users.name from Friend_list inner join users on Friend_list.userid=users.id order by rand();
To select 2 random entries try:
SELECT * FROM
(
SELECT * from users join on Friend_list.userid = users.id where users.id = ?
) as sub_equity
ORDER BY RAND() LIMIT 2
I had a same task on a project :-)
SELECT Friend_list.*, users.name
FROM Friend_list INNER JOIN users ON Friend_list.userid = users.id
ORDER BY RAND() // this will show random records
You can use ORDER BY RAND() LIMIT 3;
Try this:
SELECT * FROM friend_list f
INNER JOIN users u ON u.id = f.userid
ORDER BY rand() LIMIT 1;
SQL FIDDLE: http://sqlfiddle.com/#!2/e483c/1/0
ORDER BY RAND() is quite slow if there are many rows.
If users.id is sequential and you have statistic on users.id (e.g. MAX(users.id), MIN(users.id)), generate three random number between min, max in client side.
And following query:
SELECT u.name as person, u2.name as friend_with
FROM users u
INNER JOIN friends_list f ON u.id = f.userid
WHERE users.id IN (random_number1, 2, 3);
this query can use INDEX, so it's faster than ORDER BY RAND()
ah.. users.id would not be continuous (e.g user deleted), so you need to generate enough random number.
Try doing this:
SELECT u.name as person, u2.name as friend_with
FROM users u
INNER JOIN friends_list f ON u.id = f.userid
INNER JOIN users u2 ON u2.id = f.friend
WHERE f.userid = 1 or f.friend = 1
AND f.status = 'friends'
ORDER BY rand() LIMIT 3;
SQLFIDDLE DEMO
This will get you three random records with the name of the person and the name of his friend, being one of the userid 1
I have 3 tables.
myMembers
------------------------------------
id | username | privacy
------------------------------------
1 | userA | 0
2 | userB | 1
3 | userC | 0
4 | userD | 1
following
--------------------------------
id | user_id | follower_id
--------------------------------
1 | 2 | 1
posts
-------------------------------------
id | userID | username | statusMsg
--------------------------------------
1 | 4 | userD | Issac Newton is genius
2 | 2 | userB | Newton Saw apple
3 | 3 | userC | Newtonian Physics
4 | 1 | userA | Calculus came from Sir Newton
There is a search field. When a logged in user searches for 'keyword' in table 'posts', I want to omit results from those users who has set his privacy to '1' and WHERE searcher is not following user B.
The query should logically do this.
SELECT * from posts WHERE (match the keyword)
AND (
if (poster's privacy (which is set in myMembers)==1){
if (seacher is following poster){
select this post
}
}
else { select this post
}
)
LIMIT results to 5 rows
So for a keyword "Newton",
if userA is searching, rows 2,3,4 from 'posts' should be returned.
if userD is searching, only rows 1, 3 and 4 from 'posts' should be returned,
based on privacy and following
Edit: Tagging for future searches: IF condition within WHERE Clause in mySql
Please, try this query (also on SQL Fiddle):
SELECT p.id, p.user_id, m.username, m.privacy,
searcher.username "Searcher", p.status_msg
FROM posts p
JOIN members m ON m.id = p.user_id
LEFT JOIN following f ON p.user_id = f.user_id
JOIN members searcher ON searcher.username = 'userA'
WHERE (m.privacy = 0 OR (m.privacy = 1 AND f.follower_id = searcher.id)
OR m.id = searcher.id)
AND p.status_msg LIKE '%New%'
ORDER BY p.id
LIMIT 5;
I removed username field from posts table, as it is redundant. Also, I named tables and columns slightly different, so query might need cosmetic changes for your schema.
The first line in the WHERE clause is the one that you're looking for, it selects posts in the following order:
First posts from members without privacy;
Then posts from members that are followed by the current searcher;
Finally, posts of the member himself.
EDIT:
This query is using original identifiers:
SELECT p.id, p.`userID`, m.username, m.privacy,
searcher.username "Searcher", p.`statusMsg`
FROM posts p
JOIN `myMembers` m ON m.id = p.`userID`
LEFT JOIN following f ON p.`userID` = f.user_id
JOIN `myMembers` searcher ON searcher.username = 'userD'
WHERE (m.privacy = 0 OR f.follower_id = searcher.id OR m.id = searcher.id)
AND p.`statusMsg` LIKE '%New%'
ORDER BY p.id
LIMIT 5;
EDIT 2:
To avoid duplicates in case there're several followers for the user from the posts table, join and filtering conditions should be changed the following way (on SQL Fiddle):
SELECT p.id, p.user_id, m.username, m.privacy,
searcher.username "Searcher", p.status_msg
FROM posts p
JOIN members m ON m.id = p.user_id
JOIN members searcher ON searcher.username = 'userC'
LEFT JOIN following f ON p.user_id = f.user_id
AND follower_id = searcher.id
WHERE (m.privacy = 0 OR (m.privacy = 1 AND f.id IS NOT NULL)
OR m.id = searcher.id)
ORDER BY p.id
LIMIT 5;
Try the following:
SET #my_user_id= 1;
SELECT * FROM posts p
INNER JOIN myMembers m ON p.user_id= m.id
WHERE statusMsg LIKE '%'
AND privacy=0
AND user_id IN (SELECT follower_id FROM following f WHERE f.user_id=#my_user_id)
LIMIT 5
try this:
SELECT a.*
FROM posts a
LEFT JOIN (SELECT user_id
FROM following a1
INNER JOIN myMembers b1
ON a1.follower_id = b1.id
WHERE a1.follower_id = 1 AND
b1.privacy = 1
) b
ON a.userID = b.user_id AND
WHERE a.statusMsg LIKE '%search%' AND
b.user_id IS NULL
LIMIT 5;
or better approach without subquery:
SELECT a.*
FROM posts a
LEFT JOIN myMembers b
ON a.userID = b.id AND
b.privacy = 1
LEFT JOIN following c
ON a.userID = c.user_id AND
c.follower_id = 1
WHERE a.statusMsg LIKE '%search%' AND
b.id IS NULL AND
c.user_id IS NULL
LIMIT 5;
See: A Visual Explanation of SQL Joins