I'm trying to select Posts with the associate numbers of Comments and Likes.
This is my query
SELECT `waller_posts`.*,
COUNT(waller_comments.id) AS num_comments,
COUNT(waller_likes.id) AS num_likes
FROM `waller_posts`
LEFT JOIN `waller_comments` ON `waller_comments`.`post_id` = `waller_posts`.`id`
LEFT JOIN `waller_likes` ON `waller_likes`.`post_id` = `waller_posts`.`id`
WHERE `wall_id` = 1
AND `wall_type` = "User"
GROUP BY `waller_posts`.`id`
When I add the second left join in this case of the likes, the results of the num_comments and num_likes came wrong. How can I perform this kind of query?
The query builds up to give you every possible combination of comments and likes on a post.
Probably easiest to just use COUNT(DISTINCT...) :-
SELECT `waller_posts`.*,
COUNT(DISTINCT waller_comments.id) AS num_comments,
COUNT(DISTINCT waller_likes.id) AS num_likes
FROM `waller_posts`
LEFT JOIN `waller_comments` ON `waller_comments`.`post_id` = `waller_posts`.`id`
LEFT JOIN `waller_likes` ON `waller_likes`.`post_id` = `waller_posts`.`id`
WHERE `wall_id` = 1
AND `wall_type` = "User"
GROUP BY `waller_posts`.`id`
Note that your query is relying on a feature of MySQL but which would cause an error in most flavours of SQL. For most flavours of SQL you need to list ALL the non aggregate columns in the GROUP BY clause.
Use Distinct clause because it will display combination of like and comment table data
SELECT `waller_posts`.*,
COUNT(DISTINCT waller_comments.id) AS num_comments,
COUNT(DISTINCT waller_likes.id) AS num_likes
FROM `waller_posts`
LEFT JOIN `waller_comments` ON `waller_comments`.`post_id` = `waller_posts`.`id`
LEFT JOIN `waller_likes` ON `waller_likes`.`post_id` = `waller_posts`.`id`
WHERE `wall_id` = 1
AND `wall_type` = "User"
GROUP BY `waller_posts`.`id`
Related
I have 7 tables to work with inside a query:
tb_post, tb_spots, users, td_sports, tb_spot_types, tb_users_sports, tb_post_media
This is the query I am using:
SELECT po.id_post AS id_post,
po.description_post as description_post,
sp.id_spot as id_spot,
po.date_post as date_post,
u.id AS userid,
u.user_type As tipousuario,
u.username AS username,
spo.id_sport AS sportid,
spo.sport_icon as sporticon,
st.logo_spot_type as spottypelogo,
sp.city_spot AS city_spot,
sp.country_spot AS country_spot,
sp.latitud_spot as latitudspot,
sp.longitud_spot as longitudspot,
sp.short_name AS spotshortname,
sp.verified_spot AS spotverificado,
u.profile_image AS profile_image,
sp.verified_spot_by as spotverificadopor,
uv.id AS spotverificador,
uv.user_type AS spotverificadornivel,
pm.media_type AS mediatype,
pm.media_file AS mediafile,
GROUP_CONCAT(tus.user_sport_sport) sportsdelusuario,
GROUP_CONCAT(logosp.sport_icon) sportsdelusuariologos,
GROUP_CONCAT(pm.media_file) mediapost,
GROUP_CONCAT(pm.media_type) mediaposttype
FROM tb_posts po
LEFT JOIN tb_spots sp ON po.spot_post = sp.id_spot
LEFT JOIN users u ON po.uploaded_by_post = u.id
LEFT JOIN tb_sports spo ON sp.sport_spot = spo.id_sport
LEFT JOIN tb_spot_types st ON sp.type_spot = st.id_spot_type
LEFT JOIN users uv ON sp.verified_spot_by = uv.id
LEFT JOIN tb_users_sports tus ON tus.user_sport_user = u.id
LEFT JOIN tb_sports logosp ON logosp.id_sport = tus.user_sport_sport
LEFT JOIN tb_post_media pm ON pm.media_post = po.id_post
WHERE po.status = 1
GROUP BY po.id_post,uv.id
I am having problems with some of the GROUP_CONCAT groups:
GROUP_CONCAT(tus.user_sport_sport) sportsdelusuario is giving me the right items but repeated, all items twice
GROUP_CONCAT(logosp.sport_icon) sportsdelusuariologos is giving me the right items but repeated, all items twice
GROUP_CONCAT(pm.media_file) mediapost is giving me the right items but repeated four times
GROUP_CONCAT(pm.media_type) mediaposttype s giving me the right items but repeated four times
I can put here all tables structures if you need them.
Multiple one-to-many relations JOINed in a query have a multiplicative affect on aggregation results; the standard solution is subqueries:
You can change
GROUP_CONCAT(pm.media_type) mediaposttype
...
LEFT JOIN tb_post_media pm ON pm.media_post = po.id_post
to
pm.mediaposttype
...
LEFT JOIN (
SELECT media_post, GROUP_CONCAT(media_type) AS mediaposttype
FROM tb_post_media
GROUP BY media_post
) AS pm ON pm.media_post = po.id_post
If tb_post_media is very big, and the po.status = 1 condition in the outer query would significantly reduce the results of the subquery, it can be worth replicating the original join within the subquery to filter down it's results.
Similarly, the correlated version I mentioned in the comments can also be more performant if the outer query has relatively few results. (Calculating the GROUP_CONCAT() for each individually can cost less than calculating it for all once if you would only actually using very few of the results of the latter).
or just add DISTINCT to all the group_concat, e.g., GROUP_CONCAT(DISTINCT pm.media_type)
I'm trying to left join the second table useri_ban based on the users' ids, with the extra condition: useri_ban.start_ban = max_start.
In order for me to calculate max_start, I have to run the following subquery:
(SELECT MAX(ub.start_ban) AS max_start, user_id FROM useri_ban ub WHERE ub.user_id = useri.id)
Furthermore, in order to add max_start to every row, I need to inner join this subquery's result into the main result. However, it seems that once I apply that join, the subquery is no longer able to access useri.id.
What am I doing wrong?
SELECT
useri.id as id,
useri.email as email,
useri_ban.warning_type_id as warning_type_id,
useri_ban.type as type,
useri.created_at AS created_at
FROM `useri`
inner join
(SELECT MAX(ub.start_ban) AS max_start, user_id FROM useri_ban ub WHERE ub.user_id = useri.id) `temp`
on `useri`.`id` = `temp`.`user_id`
left join `useri_ban` on `useri_ban`.`user_id` = `useri`.`id` and `useri_ban`.`start_ban` = `max_start`
Does this solve your problem? You need GROUP BY in the inner query instead of another join.
SELECT useri.id, useri.email, maxQuery.maxStartBan
FROM useri
INNER JOIN
(
SELECT useri_ban.user_id ubid, MAX(useri_ban.startban) maxStartBan
FROM useri_ban
GROUP BY useri_ban.user_id
) AS maxQuery
ON maxQuery.ubid = useri.id;
SELECT *
FROM notifications
INNER JOIN COMMENT
ON COMMENT.id = notifications.source_id
WHERE idblog IN (SELECT blogs_id
FROM blogs
WHERE STATUS = "active")
INNER JOIN reportmsg
ON reportmsg.msgid = notifications.source_id
WHERE uid =: uid
ORDER BY notificationid DESC
LIMIT 20;
Here I am INNER JOINing notifications with comment and reportmsg; then filtering content with WHERE.
But my problem is that for the first INNER JOIN [i.e, with comment], before joining notifications with comment, I want to match notifications.idblog with blogs.blogs_id and SELECT only those rows where blogs.status = "active".
For better understanding of the code above:
Here, for INNER JOIN, with comment I want to SELECT only those rows in notifications whose idblog matches blogs.blogs_id and has status = "active".
The second INNER JOIN with reportmsg needs not to be altered. I.e, it only filters through uid.
As you can see from the image below, you can just need to merge other tables to notifications table using LEFT JOIN like that:
SELECT n.notificationid, n.uid, n.idblog, n.source_id,
b.blogs_id, b.status,
c.id,
r.msgid
-- ... and the other columns you want
FROM notifications n
LEFT JOIN blogs b ON b.blogs_id = n.idblog AND b.STATUS = "active" AND n.uid =: uid
LEFT JOIN comment c ON c.id = n.source_id
LEFT JOIN reportmsg r ON r.msgid = n.source_id
ORDER BY n.notificationid DESC
LIMIT 20;
There's no need/reason to filter before the second join because you only use inner joins and then the order of joins and WHERE-conditions don't matter:
SELECT n.*, c.*, r.*
FROM notifications AS n
JOIN COMMENT as c
ON n.source_id = c.id
LEFT JOIN blogs as b
ON n.idblogs = b.blogs_id
AND B.STATUS = 'active'
JOIN reportmsg AS R
ON n.source_id = r.msgid
WHERE uid =: uid
ORDER BY notificationid DESC
LIMIT 20
You can switch the order of joins, you can move B.STATUS = 'active' into the join-condition, but all queries will return the same result. (After the edit it's a LEFT JOIN, of course now the result differs)
And of course you shouldn't use *, better list only the columns you actually need.
if query optimizer does its work, it does not matter where you put filtering statement in INNER JOIN case but in the LEFT JOIN it has effects. Putting filtering statement in LEFT JOIN conditions cause table filtered at first and joined after while putting filtering statement in WHERE clause will filter results of join. Hence, if you want to use LEFT JOIN your query must look like:
SELECT nt.*
FROM notifications nt
LEFT JOIN Blogs bg on nt.blogs_id = bg.blogs_id and bg.STATUS = "active"
LEFT JOIN COMMENT cm ON cm.id = nt.source_id
LEFT JOIN reportmsg rm ON rm.msgid = nt.source_id
WHERE uid =: uid
ORDER BY nt.notificationid DESC
LIMIT 20;
It's very unclear what you are after here.. while your table diagram is useful, you should really supply some sample data and an expected result even if it is just a couple of dummy rows for each table.
Queries work row by row, both INNER JOINs are applied to the same notification row and non-matching rows are discarded.
Any filter applies to both JOIN and any returned rows must have a match in BOTH comment and reportmsg.
Perhaps you want two LEFT JOINs that can apply different filters and guessing from the table names perhaps it could look like this:
SELECT *
FROM notifications n
LEFT JOIN blogs b
ON n.blogId = b.blogs_id
LEFT JOIN comment c
ON c.id = n.source_id
AND b.status = "Active"
LEFT JOIN reportmsg rm
ON rm.msgid = n.source_id
WHERE n.uid =: uid
AND (c.id IS NOT NULL OR rm.msgid IS NOT NULL)
ORDER BY n.notificationid DESC
LIMIT 20
You also should work on your naming convention:
notifications, comment -> pick either plural or singular table names
notifications.notificationid, comment.id -> pick adding table name to id
notificationid, source_id -> pick underscore or no separation
idblog, notificationid -> pick prepending or appending id
Currently you pretty much have to look up every id field every time you want to use one.
You should change your query to this:
SELECT *
FROM notifications
INNER JOIN comment ON comment.id = notifications.source_id
INNER JOIN reportmsg ON reportmsg.msgid=notifications.source_id
LEFT JOIN blogs ON notifications.idblog = blogs.blogs_id
WHERE blogs.status = 'active'
ORDER BY notificationid DESC
LIMIT 20;
I will try to explain things as much as I can.
I have following query to fetch records from different tables.
SELECT
p.p_name,
p.id,
cat.cat_name,
p.property_type,
p.p_type,
p.address,
c.client_name,
p.price,
GROUP_CONCAT(pr.price) AS c_price,
pd.land_area,
pd.land_area_rp,
p.tagline,
p.map_location,
r.id,
p.status,
co.country_name,
p.`show`,
u.name,
p.created_date,
p.updated_dt,
o.type_id,
p.furnished,
p.expiry_date
FROM
property p
LEFT OUTER JOIN region AS r
ON p.district_id = r.id
LEFT OUTER JOIN country AS co
ON p.country_id = co.country_id
LEFT OUTER JOIN property_category AS cat
ON p.cat_id = cat.id
LEFT OUTER JOIN property_area_details AS pd
ON p.id = pd.property_id
LEFT OUTER JOIN sc_clients AS c
ON p.client_id = c.client_id
LEFT OUTER JOIN admin AS u
ON p.adminid = u.id
LEFT OUTER JOIN sc_property_orientation_type AS o
ON p.orientation_type = o.type_id
LEFT OUTER JOIN property_amenities_details AS pad
ON p.id = pad.property_id
LEFT OUTER JOIN sc_commercial_property_price AS pr
ON p.id = pr.property_id
WHERE p.id > 0
AND (
p.created_date > DATE_SUB(NOW(), INTERVAL 1 YEAR)
OR p.updated_dt > DATE_SUB(NOW(), INTERVAL 1 YEAR)
)
AND p.p_type = 'sale'
everything works fine if I exclude GROUP_CONCAT(pr.price) AS c_price, from above query. But when I include this it just gives one result. My intention to use group concat above is to fetch comma separated price from table sc_commercial_property_price that matches the property id in this case p.id. If the records for property exist in sc_commercial_property_price then fetch them in comma separated form along with other records. If not it should return blank. What m I doing wrong here?
I will try to explain again if my problem is not clear. Thanks in advance
The GROUP_CONCAT is an aggregation function. When you include it, you are telling SQL that there is an aggregation. Without a GROUP BY, only one row is returns, as in:
select count(*)
from table
The query that you have is acceptable syntax in MySQL but not in any other database. The query does not automatically group by the columns with no functions. Instead, it returns an arbitrary value. You could imagine a function ANY, so you query is:
select any(p.p_name) as p_num, any(p.tagline) as tagline, . . .
To fix this, put all your current variables in a group by clause:
GROUP BY
p.p_name,
p.id,
cat.cat_name,
p.property_type,
p.p_type,
p.address,
c.client_name,
p.price,
pd.land_area,
pd.land_area_rp,
p.tagline,
p.map_location,
r.id,
p.status,
co.country_name,
p.`show`,
u.name,
p.created_date,
p.updated_dt,
o.type_id,
p.furnished,
p.expiry_date
Most people who write SQL think it is good form to include all the group by variables in the group by clause, even though MySQL does not necessarily require this.
Add GROUP BY clause enumerating whatever you intend to have separate rows for. What happens now is that it picks some value for each result column and group_concats every pr.price.
I have a litte problem with a mysql query.
I use 5 tables:
user_has_data (uid, dataid); users (uid, uname); user_in_group(uid, groupid, data); groups(groupid, data, packageid); packages(packageid, name)
all ids are PK. I want to build a sql query that finds a user, which belongs to a specified dataid, by its uname and checks if the user is in a group (relation in table user_in_group) belonging to a specified package (a group is assigned to one package). if so data from users, package and group should be fetched, otherwise only the user data should be fetched. Therefore I use left joins, so I can also get the users with no group:
SELECT `uac`.`uid`, `u`.`uid`, `uig`.`groupid`, `ag`.`packageid`
FROM `user_has_data` AS `uac`
INNER JOIN `users` AS `u` ON u.uid = uac.uid
LEFT JOIN `user_in_group` AS `uig` ON uig.uid = uac.uid
LEFT JOIN `groups` AS `ag` ON (ag.groupid = uig.groupid) AND (ag.packageid = 2)
WHERE (uac.dataid = '3') AND (u.uname LIKE 'test%')
GROUP BY `u`.`uid`
Unfortunately I get wrong results: I get groups that have a different packageid than stated in the join, if the user has another group assigned to him with a different packageid.
probably this is because the first left join has no restrictions to packageid and the second is a left join and so it has no restrictions on the result (packageid is NULL for all results, but should have values). If I change the second left join to a ordinary join, the group problem would be fixed but the query cant find users without group any more.
Any ideas how to fix this or even possible?
thanks in advance!
Are you saying that you are actually seeing the value ag.packageid = 2 in your query results?
If not, I think you might try something like:
SELECT `uac`.`uid`, `u`.`uid`, `g`.`groupid`, `g`.`packageid`
FROM `user_has_data` AS `uac`
INNER JOIN `users` AS `u` ON u.uid = uac.uid
LEFT JOIN (`user_in_group` AS `uig`
INNER JOIN `groups` AS `ag` ON (ag.groupid = uig.groupid) AND (ag.packageid = 2) )
AS `g` ON uac.uid = g.uid
WHERE (uac.dataid = '3') AND (u.uname LIKE 'test%')
GROUP BY `u`.`uid`
Because you are limiting your search to a specific group packageid of '2', why not just make both of your LEFT JOIN INNER JOINS and then throw in ag.packageid = 2 in your WHERE clause?
SELECT `uac`.`uid`, `u`.`uid`, `uig`.`groupid`, `ag`.`packageid`
FROM `user_has_data` AS `uac`
INNER JOIN `users` AS `u` ON u.uid = uac.uid
LEFT OUTER JOIN `user_in_group` AS `uig` ON uig.uid = uac.uid
LEFT OUTER JOIN `groups` AS `ag` ON ag.groupid = uig.groupid
WHERE (uac.dataid = '3') AND (u.uname LIKE 'test%')
AND (ag.packageid = 2 OR uig.uid IS NULL)
GROUP BY `u`.`uid`
I know LEFT JOIN and LEFT OUTER JOIN mean the same thing, but I like to be explicit. With the condition in your join, I bet you were getting groups with different packages, but weren't getting the packages?