I'm attempting to update a MySQL table to show column name 'processed' as '2' if there is duplicate entries for 'name' and 'address_1', but it's not working - as usual I think I'm just being a bit of a moron..
Here's what I'm trying
UPDATE `records`
SET `processed`='2', `count` = (SELECT COUNT(`user`)
FROM `records`
WHERE `name`<>''
AND `address_1`<>'')
WHERE `count`=> '1';
Basically, if there's more than one 'name' and 'address_1' then the 'processed' field needs updating to '2'..
You could use a query like this one to return duplicated names and addresses:
SELECT name, address_1, COUNT(*) cnt
FROM records
GROUP BY name, address_1
HAVING COUNT(*)>1
and then join this query to the records table, and update the column processed to 2 where the join succeeds:
UPDATE
records INNER JOIN (SELECT name, address_1, COUNT(*) cnt
FROM records
GROUP BY name, address_1
HAVING COUNT(*)>1) duplicates
ON records.name = duplicates.name
AND records.address_1=duplicates.address_1
SET
`processed`='2',
`count` = duplicates.cnt
WHERE
records.`name`<>''
AND records.`address_1`<>''
Related
I have a query in MySQL based on which I am finding duplicate records of some columns.
select max(id), count(*) as cnt
from table group by start_id, end_id, mysqltable
having cnt>1;
This above query gives me the max(id) and the count of number of records that have start_id,end_id,mysqltable column values same.
I want to delete all the records that match the max(id) column of the above query
How can I do that?
I have tried like below
delete from table
where (select max(id), count(*) as cnt
from table group by start_id,end_id,mysqltable
having cnt>1)
But Unable to delete records
You can remove duplicate records using JOIN.
DELETE t1 FROM table t1
INNER JOIN
table t2
WHERE
t1.id > t2.id AND t1.start_id = t2.start_id AND t1.end_id = t2.end_id AND t1.mysqltable = t2.mysqltable;
This query keeps the lowest id and remove the highest.
I think so this command should work:
delete from table
where id in
( select max(id) from table
group by start_id, end_id, mysqltable
having count(*) > 1
);
I am not sure how to do this in mysql, i have searched but I can't seem to find a solution.
,
I have a table like so.
id pid occurrence
1 23 blank
2 23 blank
3 44 blank
Basically, occurrence should have the value of 2, for id 1,2 and a value of 1 for id 3.
Any help would be appreciated. I can easily call count and GROUP BY, and get the number of times each one occurance, but I would like to update column occurrence in the right place for each pid.
To get the correct occurrence value you can do
select pid, count(*) as occurrence
from your_table
group by pid
To update the table do
update your_table t1
join
(
select pid, count(*) as occurrence
from your_table
group by pid
) t2 on t1.pid = t2.pid
set t1.occurrence = t2.occurrence
If you want to set the value in the table, use update with a join:
update table t join
(select pid, count(*) as cnt
from table
group by pid
) tt
on tt.pid = t.pid
set t.occurrence = tt.cnt;
I have the query below that shows me duplicates in my table. I would like to know how can i turn this into a delete query to delete these duplicate rows but leaving just one. My table does have a auto increment id column.
SELECT * FROM tbl_user_tmp AS t1
INNER JOIN (
SELECT name, activity, class, COUNT(1) AS cnt FROM tbl_user_tmp
WHERE user = 'test' AND disregard = 0
GROUP BY name, activity, class
HAVING cnt > 1
) AS t2
ON t1.name = t2.name AND t1.activity = t2.activity AND t1.class = t2.class
WHERE user = 'test' AND disregard = 0
GROUP BY t1.name, t1.activity, t1.class
I have tried the query below and seems to work, but im afraid im missing something. does it look correct?
delete from tbl_user_tmp
where user='test' AND id not in
(
select minid from
(select min(id) as minid from tbl_user_tmp where user='test' group by name, activity, class) as newtable
)
You can use LIMIT.
Example:
DELETE FROM users
LIMIT 2;
Now you just need to set COUNT - 1 as your limit ;)
I have a table full of duplicate data, based on multiple columns. I came up with this query to find all the duplicated rows
select *
from polls
group by server_id, product_id, poll_date
having count(*) > 1;
How do I update these results and set the "updated_by" field to "admin".
I tried doing this, but it doesn't work for me :(
update polls
set updated_by='admin'
group by server_id, product_id, poll_date
having count(*) > 1;
Thanks for your help
You should be able to join your SELECT with the UPDATE.
UPDATE `polls` AS `p1`
INNER JOIN (
SELECT *
FROM `polls`
GROUP BY `server_id`, `product_id`, `poll_date`
HAVING COUNT(*) > 1
) AS `p2`
ON `p2`.`server_id` = `p1`.`server_id`
AND `p2`.`product_id` = `p1`.`product_id`
AND `p2`.`poll_date` = `p1`.`poll_date`
SET `p1`.`updated_by` = 'admin';
Of course it would be better to directly join on the primary key (if you have one).
I am updating my table setting a field named "status" based on the condition that the total number of distinct rows should be more than 10 and less than 13. The query is as follows:
update myTable set status='Established'
where id IN(select id, count(*) as c
from myTable
where year>=1996 and year<=2008
group by id
having count(distinct year)>=10 and count(distinct year)<=13)
The problem is, I'm getting error1241 that is "operand should contain 1 column"! Could you please advise how can I solve this? Thanks!
The result of the sub query must return only 1 column :
update myTable set status='Established'
where id IN(select id
from myTable
group by id
having count(distinct year)>=10 and count(distinct year)>=13)
In MySQL, an update with a join often performs better than an update with a subquery in the where clause.
This version might have better performance:
update myTable join
(select id, count(*) as c
from myTable
where year >= 1996 and year <= 2008
group by id
having count(distinct year) >= 10 and count(distinct year) <= 13
) filter
on myTable.id = filter.id
set status = 'Established';
I will also note that you have a table where a column called id is not unique among the rows. Typically, such a column would be a primary key, so the having clause would always fail (there would only be one row).
update myTable
set status='Established'
where id IN(select id from myTable
group by id
having count(distinct year)>=10
and count(distinct year)>=13)
You are using IN operator and then you inner query returns two columns id and count(*) it should return only one column back.