Delete from post
where id_post
in
(
select MIN(id_post)
from post
where id_owner='2'
)
Returns:
"You can't specify target table 'post' for update in FROM clause"
What am I doing wrong?
The problem is that MySQL, if you're doing an UPDATE/INSERT/DELETE on a table, you can't reference that table in an inner query (you can however reference a field from that outer table...)
The solution is to replace the instance of post in the sub-query with (select MIN(id_post)
from post
where id_owner='2' ), like this
Delete from post
where id_post
in
(
select id_post
from (select MIN(id_post)
from post
where id_owner='2') as A
)
How about using ORDER BY and LIMIT?
Delete p
from post p
where id_owner = 2
order by id_post
limit 1;
Note: Don't use single quotes around numeric constants. I am guessing id_owner is numeric.
Related
I need to finish the select query below. The query shows me the count of comments with the same comment_id.I just ultimately want to delete the duplicates and leave the non duplicates alone.This is a wordpress database
screenshot of my current query results
SELECT `comment_ID`, `comment_ID`, count(*) FROM `wp_comments` GROUP BY `comment_ID` HAVING COUNT(*) > 1 ORDER BY `count(*)` ASC
example of 2 entries I need to delete one
First back up your bad table in case you goof something up.
CREATE TABLE wp_commments_bad_backup SELECT * FROM wp_comments;
Do you actually have duplicate records here (duplicate in all columns) ? If so, try this
CREATE TABLE wp_comments_deduped SELECT DISTINCT * FROM wp_comments;
RENAME TABLE wp_comments TO wp_comments_not_deduped;
RENAME TABLE wp_comments_deduped TO wp_comments;
If they don't have exactly the same contents and you don't care which contents you keep from each pair of duplicate rows, try something like this:
CREATE TABLE wp_comments_deduped
SELECT comment_ID,
MAX(comment_post_ID) comment_post_ID,
MAX(comment_author) comment_author,
MAX(comment_author_email) comment_author_email,
MAX(comment_author_url) comment_author_url,
MAX(comment_author_IP) comment_author_IP,
MAX(comment_date) comment_date,
MAX(comment_date_gmt) comment_date_gmt,
MAX(comment_content) comment_content,
MAX(comment_karma) comment_karma,
MAX(comment_approved) comment_approved,
MAX(comment_agent) comment_agent,
MAX(comment_type) comment_type,
MAX(comment_parent) comment_parent,
MAX(user_id) user_id
FROM wp_comments
GROUP BY comment_ID;
RENAME TABLE wp_comments TO wp_comments_not_deduped;
RENAME TABLE wp_comments_deduped TO wp_comments;
Then you'll need to doublecheck whether your deduplicating worked:
SELECT comment_ID, COUNT(*) num FROM wp_comments GROUP BY comment_ID;
Then, once you're happy with it, put back WordPress's indexes.
Pro tip: Use a plugin like Duplicator when you migrate from one WordPress setup to another; its authors have sorted out all this data migration for you.
I would recommand add a unique key to the table make it auto incremental call it tempId , so you would be able to to distinguish between one duplicate set, use below query to remove duplicate copies and at the end remove that '`tempid' column:
DELETE FROM `wp_comments`
WHERE EXISTS (
SELECT `comment_ID` , MIN(`tempid`) AS `tempid`
FROM `wp_comments` as `dups`
GROUP BY `comment_ID`
HAVING
COUNT(*) > 1
AND `dups`.`comment_ID` = `wp_comments`.`comment_ID`
AND `dups`.`tempid` = `wp_comments`.`tempid`
)
I'm not clear on why there appear to be two different fields both named 'column_ID' from the same table, but I believe this will delete only the first of the two identical records. Before running a DELETE statement, however, be sure to make a backup of the original table.
DELETE
TOP 1 *
FROM
'wp_comments'
WHERE
comment_ID IN
(
SELECT
comment_ID,
r,
(comment_ID + '_' + r) AS unique
FROM
(
SELECT
`comment_ID`,
`comment_ID`,
RANK() OVER (PARTITION BY 'comment_id' ORDER BY 'comment_id') AS r
FROM
'wp_comments'
)
WHERE
r>1
)
i am trying to do a mysql query to update a table with some values in order of ID, i have sucess in the first time (generate 38 result row) but when i execute this again, this multiplicate the existing value in the table (38x38 = 1444 row result) repeting the already existing product_id in new ID rows.....
i want to insert to this table, only unique product_id from the another target table, and group by the ID [1,2,3,4,5, and dont repeat this too]
the code:
/* add all eligible customers to temporary table */
INSERT INTO `temp_wp_woocommerce_subscription_downloads`
(`product_id`, `subscription_id`)
SELECT posts.ID AS product_id, downn.subscription_id AS subscription_id
FROM wp_posts posts
JOIN wp_woocommerce_subscription_downloads downn
WHERE posts.post_type = 'product'
AND posts.post_status = 'publish'
;
in the print you can see the generated issue:
(https://prntscr.com/s2zhil)
EDIT: Work perfect with the code from the #GordonLinoff answer,but after run and add a new product and run the query again the ID is dont by a order (appear to "jump/burn some ids", how i order by unique id's too? and as you can see :
http://prntscr.com/s31rrq
This addresses the original version of the question.
You can add a unique index on productid and then use on duplicate key.
alter table temp_wp_woocommerce_subscription_downloads
add constraint unq_temp_wp_woocommerce_subscription_downloads_product_id
unique(product_id);
INSERT INTO temp_wp_woocommerce_subscription_downloads(`product_id`, `subscription_id`)
SELECT p.ID AS product_id, d.subscription_id AS subscription_id
FROM wp_posts posts p JOIN
wp_woocommerce_subscription_downloads d
ON p.post_type = 'product' AND p.post_status = 'publish'
ON DUPLICATE KEY UPDATE subscription_id = d.subscription_id;
That said, I suspect that you might also be missing a JOIN condition on the table -- say by post or product.
I have been trying to do this in many ways suggested.
Note: we do not want aggregate function or Partition since this is just a small part of whole Stored procedure and this is client requirement to not have it, so not in option and not possible duplicate of other existing answers / questions
I have a messages table, which has a column from and to, a foreign key to the user table, basically which user sends to whom at simplest. I also have other columns which are isSnoozed and snoozeAt for if the message is snoozed.
So the ordering is according to case. If messages is snoozed then consider snoozeAt time to Order or if not then consider sendAt. (right now we can ignore this condition while ordering, But I mentioned this since we cannot take simply MAX(id) )
I need to get recent most message from messages group by from user id
messages table like :
id -- to -- from -- isSnoozed -- snoozedAt -- sendAt ...
What I tried :
select * from ( select * from messages order by sendAt DESC) as TEMP GROUP BY TEMP.from
I tried many similar approaches but none worked.
I wasted many paid hours but can't find an approach which meets my exact requirement
NOTE: Please ignore typo in query if any, since I cant type in exact query table and names, So i typed in directly here
I figured this out by doing something like this, which could be explained in a simplified way:
select * from message where message.id in (
select
( select id from message where message.from = user.id order by CASE isSnoozed WHEN 0 THEN sendAt ELSE snoozeAt END DESC limit 1) as id
from user where user.id in ( select friends.`whoIsAdded` from friends where friends.`whoAdded` = myId)
) order by CASE isSnoozed WHEN 0 THEN sendAt ELSE snoozeAt END DESC
If I understand correctly, you just want the largest value in one of two columns. Assuming the values are never NULL, you can use greatest():
select m.*
from messages m
where greatest(m.sendAt, m.snoozedAt) =
(select max(greatest(m2.sendAt, m2.snoozedAt))
from messages m2
where m2.from = m.from
);
If the columns can be NULL, then you can use coalesce() to give them more reasonable values.
I got two MySQL working fine and i'm trying to find a way to combine them into one single query.
First, it selects ID of an employee.
SELECT 'ID' FROM `employee` ORDER BY ID DESC LIMIT 1;
Let's say it returns ID 100;
Then update data of employees whose ID is 100
UPDATE 'LOG' SET `TIME_EXIT`='2013/02/22' WHERE `ID`='100';
Can i do it all in a single query?
Just add them together:
UPDATE LOG SET TIME_EXIT = '2013/02/22'
WHERE ID = (
SELECT ID
FROM employee
ORDER BY ID DESC
LIMIT
);
But based on that code currently it'll only ever update the last employee, you will need to select the correct employee by using some other identifier to ensure you have the correct one.
UPDATE LOG SET TIME_EXIT = '2013/02/22'
WHERE ID = (
SELECT ID
FROM employee
WHERE NAME = 'JOHN SMITH'
ORDER BY ID DESC
LIMIT 1
);
It's now a few months old, but maybe helps you or others finding this via google…
If you want to UPDATE a field in the same selected table use this:
UPDATE LOG SET
TIME_EXIT = '2013/02/22'
WHERE ID = (
SELECT ID
FROM (
SELECT ID
FROM LOG
WHERE whatEverYouWantToCheck = whateverYouNeed
) AS innerResult
)
So, you SELECT id from a subselect. If you try to subselect it directly, mySQL quites with your error message You can't specify target table 'log' for update in FROM clause, but this way you hide your subsubquery in a subquery and that seems to be fine. Don't forget the AS innerResult to avoid getting the error message #1248 - Every derived table must have its own alias. Also match the subsubquery field name to the subquery field name in case you do something like SELECT COUNT(*) or SELECT CONCAT('#', ID)
I am trying to replicate a forum function by getting the last reply of a post.
For clarity, see PHPBB: there are four columns, and the last column is what I like to replicate.
I have my tables created as such:
discussion_id (primary key)
user_id
parent_id
comment
status
pubdate
I was thinking of creating a Link Table that would update for each time the post is replied to.
The link table would be as follow:
discussion_id (primary key)
last_user_id
last_user_update
However, I am hoping that theres a advance query to achieve this method. That is, grabbing each Parent Discussion, and finding the last reply in each of those Parent Discussions.
Am I right that there is such a query?
Here is a update.
I am still having a little trouble but I feel like I am almost there.
My current query:
SELECT
`discussion_id`,
`parent_id`,
`user_id` as `last_user_id`,
`user_name` as `last_user_name`
FROM `table1`, `table2`
WHERE `table1`.`id` = `table2`.`user_id`
Results:
discussion_id---------parent_id-----last_user_id-------last_user_name
30---------------------NULL-------------3--------------raiku
31---------------------30---------------2--------------antu
32---------------------30---------------1--------------admin
33---------------------NULL-------------3--------------raiku
Adding this:
GROUP BY `parent_id`
Turns it into:
discussion_id---------parent_id-----last_user_id-------last_user_name
32---------------------30---------------1--------------admin
33---------------------NULL-------------3--------------raiku
But I want it to turn it into:
discussion_id---------parent_id-----last_user_id-------last_user_name
30---------------------NULL-------------3--------------raiku
32---------------------30---------------1--------------admin
33---------------------NULL-------------3--------------raiku
Id 30, and ID 33 share the same parent_id: NULL but they are the "starting thread" or the "parent post"
They should not be combined, how would I go on by "Grouping" but "ignoring" null values?
This query will take the highest (thus assuming latest) discussion per parent_id. Not the neatest solution however ...
select discussion_id, user_id, pubdate
from tablename
where discussion_id in
(
select max(discussion_id)
from tablename
group by parent_id
)
You could try something like this:
SELECT parent.discussion_id,
child.discussion_id as last_discussion_id,
child.user_id as last_user_id,
child.pubdate as last_user_update
FROM Discussion parent
INNER JOIN Discussion child ON ( child.parent_id = parent.discussion_id )
LEFT OUTER JOIN Discussion c ON ( c.parent_id = parent.discussion_id AND c.discussion_id > child.discussion_id)
WHERE c.discussion_id IS NULL
The left join to Discussion c will not match when you have the post with the highest id, which should be the row that you want.
You want GROUP BY. This should work out OK:
SELECT MAX(`pubdate`), `discussion_id`, `user_id` FROM `table` GROUP BY `parent_id`
You'll obviously need to fill in an appropriate the WHERE clause and LIMIT as needed.