I have a huge table of mysqlwhich contains more than 33 million records .How I could compare my table to found non duplicate records , but unfortunately select statement doesn't work. Because it's huge table.
Please provide me a solution
First, Create a snapshot of your database or the tables you want to compare.
Optionally you can also limit the range of data you want to compare , for example only 3 years of data. This way your select query won't hog all the resources.
Snapshot will be bunch of files each representing a table containg your primary key or business key for each record ( I am assuming you can compare data based on aforementioned key . If thats not the case record all the field in your file)
Next, read each records from the file and do a select against the corresponding table. If there are more than 1 record you know it is a duplicate
Thanks
Look at the explain plan and see if what the DB is actually doing for the NOT IN.
You could try refactoring, with an index on subscriber as Roy suggested if necessary. I'm not familiar enough with MySQL to know whether the optimizer will execute these identically.
SELECT *
FROM contracts
WHERE NOT EXISTS
( SELECT 1
FROM edms
WHERE edms.subscriber=contracts.subscriber
);
-- or
SELECT C.*
FROM contracts AS C
LEFT
JOIN edms AS E
ON E.subscriber = C.subscriber
WHERE E.subscriber IS NULL;
Good morning.
I have a table on MySQL DataBase.
In this table there are 5 robots that can write like 10 record each per hour.
Every 3 month a script that I have created, make a copy of the table and then delete all the table entries (In this way I can keep the IDs in a certain order).
My question is.
That are two different statement:
CREATE TABLE omologationResult_{date} AS SELECT * FROM omologationResult
DELETE FROM omologationResult
if the script is going to copy the table at point 0, and a record will be added from the robots, there's no problem, because the SQL statement starts from the lowest ID 'till the end. But if the script is going to delete the table and the robot is writing in it. What will happen? I lose the last robot record?
And if it's true. What can I do to make a copy of the table and then remove only the data that I've copied?
Thank you
Yes, this is not a safe operation because it's not atomic. It's quite possible for another thread to insert values into that table in between your CREATE .. SELECT and the DELETE. One option you have is to use a multi table DELETE
CREATE TABLE omologationResult_{date} AS SELECT * FROM omologationResult;
DELETE omologationResult FROM omologationResult
INNER JOIN omologationResult_{date} ON omologationResult_{date}.id = omologationResult.id
Will ensure that only items that exist in both tables have been deleted from omologationResult
I wish to duplicate a selection of records in a mySQL table.
The pk of the table is an autoincremented int.
I want to do this with one set of mysql queries (for performance reasons).
It seems like the fastest way to do this is to put the results of the selection into a temporary table,
make any changes needed, and reinsert the records back to the original table, like this:
CREATE TEMPORARY TABLE temp1234 ENGINE=MEMORY SELECT * FROM a_table WHERE column='my selection';
# do updates in temp1234; (altering FK's mainly)
INSERT INTO a_table SELECT * FROM temp1234;
But when I try to do this i get an error for duplicate PKs.
Now, I realise that I could alter the INSERT with SELECT query to exclude the pk/ID column, but as I am proceduraly generating these queries across multiple tables for a large data copying function, i want to avoid having to supply column names.
What is the best way around this problem?
I have this query that works fine. Its deletes records that are old based on current time.
$cleanacc_1 = "DELETE FROM $acc_1
WHERE `Scheduled` < DATE_SUB(UTC_TIMESTAMP(), INTERVAL 30 SECOND)";
$result = mysql_query($cleanacc_1);
However, there are over 100 tables (accounts) that need deleting and I was wondering if I can combine them into one query. If possible how?
This implies you create a new table for every account. Why are you not creating a record for each account within a single table?
For example...
create table account (id int unsigned primary key auto_increment, other fields...);
If you alter your table structure you will be able to delete individual account records with a single query...
delete from account where condition=true;
Individual transaction records for each account are then stored in another table and contain the account id they relate to...
create table transaction (id, account_id, other transaction fields);
If you don't change the database design you'll need to write PHP code that loops through each table and runs your delete query. This is very inefficient and I urge you to redesign the table as suggested.
If you don't understand why my table redsign suggestion is a better approach, post more information about your database and I'll explain in more detail with a working example.
No way to do that, AFAIK; anyways, I don't think it would be a big problem to run 100 queries, assuming you are not running that for each request or so..
Are you expecting performance issues? If that's the case, I'd probably use a cron job to run that query every X minutes..
You could setup a view of the tables and do then run the delete sql against the view. That should delete the underlying table data as well. Your table schema and permissions could have an affect whether this will work or not. Check out this answer, it might help as well.
Does deleting row from view delete row from base table - MYsql?
Please consider the following example.
I have three tables in following structure.
Table names : t1,t2,t3
Fields : Id, name
Im going to perform delete query with one condition which recode id must less than 10.
DELETE FROM t1, t2,t3 USING t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.id<10 and t2.id<10 and t3.id<10.
The query has been successfully executed ( MySql ). I got the expected output.
So please try the same way with your condition.
I got a table with a normal setup of auto inc. ids. Some of the rows have been deleted so the ID list could look something like this:
(1, 2, 3, 5, 8, ...)
Then, from another source (Edit: Another source = NOT in a database) I have this array:
(1, 3, 4, 5, 7, 8)
I'm looking for a query I can use on the database to get the list of ID:s NOT in the table from the array I have. Which would be:
(4, 7)
Does such exist? My solution right now is either creating a temporary table so the command "WHERE table.id IS NULL" works, or probably worse, using the PHP function array_diff to see what's missing after having retrieved all the ids from table.
Since the list of ids are closing in on millions or rows I'm eager to find the best solution.
Thank you!
/Thomas
Edit 2:
My main application is a rather easy table which is populated by a lot of rows. This application is administrated using a browser and I'm using PHP as the intepreter for the code.
Everything in this table is to be exported to another system (which is 3rd party product) and there's yet no way of doing this besides manually using the import function in that program. There's also possible to insert new rows in the other system, although the agreed routing is to never ever do this.
The problem is then that my system cannot be 100 % sure that the user did everything correct from when he/she pressed the "export" key. Or, that no rows has ever been created in the other system.
From the other system I can get a CSV-file out where all the rows that system has. So, by comparing the CSV file and my table I can see if:
* There are any rows missing in the other system that should have been imported
* If someone has created rows in the other system
The problem isn't "solving it". It's making the best solution to is since there are so much data in the rows.
Thanks again!
/Thomas
We can use MYSQL not in option.
SELECT id
FROM table_one
WHERE id NOT IN ( SELECT id FROM table_two )
Edited
If you are getting the source from a csv file then you can simply have to put these values directly like:
I am assuming that the CSV are like 1,2,3,...,n
SELECT id
FROM table_one
WHERE id NOT IN ( 1,2,3,...,n );
EDIT 2
Or If you want to select the other way around then you can use mysqlimport to import data in temporary table in MySQL Database and retrieve the result and delete the table.
Like:
Create table
CREATE TABLE my_temp_table(
ids INT,
);
load .csv file
LOAD DATA LOCAL INFILE 'yourIDs.csv' INTO TABLE my_temp_table
FIELDS TERMINATED BY ','
LINES TERMINATED BY '\n'
(ids);
Selecting records
SELECT ids FROM my_temp_table
WHERE ids NOT IN ( SELECT id FROM table_one )
dropping table
DROP TABLE IF EXISTS my_temp_table
What about using a left join ; something like this :
select second_table.id
from second_table
left join first_table on first_table.id = second_table.id
where first_table.is is null
You could also go with a sub-query ; depending on the situation, it might, or might not, be faster, though :
select second_table.id
from second_table
where second_table.id not in (
select first_table.id
from first_table
)
Or with a not exists :
select second_table.id
from second_table
where not exists (
select 1
from first_table
where first_table.id = second_table.id
)
The function you are looking for is NOT IN (an alias for <> ALL)
The MYSQL documentation:
http://dev.mysql.com/doc/refman/5.0/en/all-subqueries.html
An Example of its use:
http://www.roseindia.net/sql/mysql-example/not-in.shtml
Enjoy!
The problem is that T1 could have a million rows or ten million rows, and that number could change, so you don't know how many rows your comparison table, T2, the one that has no gaps, should have, for doing a WHERE NOT EXISTS or a LEFT JOIN testing for NULL.
But the question is, why do you care if there are missing values? I submit that, when an application is properly architected, it should not matter if there are gaps in an autoincrementing key sequence. Even an application where gaps do matter, such as a check-register, should not be using an autoincrenting primary key as a synonym for the check number.
Care to elaborate on your application requirement?
OK, I've read your edits/elaboration. Syncrhonizing two databases where the second is not supposed to insert any new rows, but might do so, sounds like a problem waiting to happen.
Neither approach suggested above (WHERE NOT EXISTS or LEFT JOIN) is air-tight and neither is a way to guarantee logical integrity between the two systems. They will not let you know which system created a row in situations where both tables contain a row with the same id. You're focusing on gaps now, but another problem is duplicate ids.
For example, if both tables have a row with id 13887, you cannot assume that database1 created the row. It could have been inserted into database2, and then database1 could insert a new row using that same id. You would have to compare all column values to ascertain that the rows are the same or not.
I'd suggest therefore that you also explore GUID as a replacement for autoincrementing integers. You cannot prevent database2 from inserting rows, but at least with GUIDs you won't run into a problem where the second database has inserted a row and assigned it a primary key value that your first database might also use, resulting in two different rows with the same id. CreationDateTime and LastUpdateDateTime columns would also be useful.
However, a proper solution, if it is available to you, is to maintain just one database and give users remote access to it, for example, via a web interface. That would eliminate the mess and complication of replication/synchronization issues.
If a remote-access web-interface is not feasible, perhaps you could make one of the databases read-only? Or does database2 have to make updates to the rows? Perhaps you could deny insert privilege? What database engine are you using?
I have the same problem: I have a list of values from the user, and I want to find the subset that does not exist in anther table. I did it in oracle by building a pseudo-table in the select statement Here's a way to do it in Oracle. Try it in MySQL without the "from dual":
-- find ids from user (1,2,3) that *don't* exist in my person table
-- build a pseudo table and join it with my person table
select pseudo.id from (
select '1' as id from dual
union select '2' as id from dual
union select '3' as id from dual
) pseudo
left join person
on person.person_id = pseudo.id
where person.person_id is null