I have an INSERT query which looks like:
$db->Query("INSERT INTO `surfed` (user, site) VALUES('".$data['id']."', '".$id."')");
Basically I want to insert just like the above query but if the site is already submitted by another user I don't want it to then re-submit the same $id in to the site column. But multiple users can view the same site and all users need to be in the same row as the site that they have viewed which causes the surfed table to have 10s of thousands of inserts which dramatically slows down the site.
Is there any way to maybe split up the insert in some way so that if a site is already submitted it won't then submit it again for another user. Maybe there's a way to use UPDATE so that there isn't an overload of inserts?
Thanks,
I guess the easiest way to do it would be setting up a stored procedure which executes a SELECT to check if the user-site-combination is already in the table. If not, you execute the insert statement. If that combination already exist, you're done and don't execute the insert.
Check out the manual on stored procedures
http://dev.mysql.com/doc/refman/5.1/en/create-procedure.html
You need to set a conditional statement that asks whether the id already exists then if it does update otherwise insert
If you don't need to know whether you actually inserted a line, you can use INSERT IGNORE ....
$db->Query("INSERT IGNORE INTO `surfed` (user, site) VALUES('".$data['id']."', '".$id."')");
But this assumes that you have a unique key defined for the columns.
IGNORE here will ignore the Integrity constraint violation error triggered by attempting to add the same unique key twice.
The MySQL Reference Manual on the INSERT syntax has some informations on that http://dev.mysql.com/doc/refman/5.5/en/insert.html
Related
This question already has answers here:
How can I do 'insert if not exists' in MySQL?
(11 answers)
Closed 1 year ago.
I found a not so nice method for checking if there a row already exists, and if it does exists, then it doesn't add it to avoid duplicates. Am i completely crazy to rely on this method or should i go old fashioned way where i check if it exists BEFORE trying to insert row in database?
The table is VERY simple :)
-ID [PK]
-Message
-Hashed_message [UNIQUE] (stored procedure, takes message and hashes it upon insert)
Now when i try to insert a new row i would say
*`insert into .... message = xxx
Upon insertion mysql will create a hash on message automatically, but since it's an unique column, incase the hash already exists in database, it will simply throw an error, and no duplicates will exist ever... i hope.
The reason for using hashes, is simply to avoid checking duplicates by scanning every large message, instead i though a short hash would be easier to check for duplicates.
So is this method bad for avoiding duplicates?
I mean i could before insert, manually create that hash of my message and check if that hash exists and THEN insert the message, but i would hope to avoid always trying to match the stored procedure function on PHP as well.
quick note: there is a similar thread about insert and then ignoring error on duplicate, but this one is related to how it is handled when a derived column(Stored procedure) is used to accomplish this
If the hashed message has to be unique, create a key on that column with the UNIQUE constrain: so there won't be two rows with the same hash.
Then, when you insert a new row modify your query with the following:
INSERT INTO table SET message='$message', hashed_message='$hashed_message'
ON DUPLICATE KEY id=id;
This will perform an insert if the hashed_message is unique. Otherwise will not do any update.
If you want to update something in case of duplicate your query will become:
INSERT INTO table SET message='$message', hashed_message='$hashed_message'
ON DUPLICATE KEY UPDATE message='$updated_message'
just to make an example.
Note that this method won't raise any exception in case of duplicate values: you need extra logic if you need to perform actions in your frontend in case of duplicates (i.e. message shown to the user).
More details here
I have a query that runs everytime a user logins. Since this query regards information the user might have third-party updated recently I thought it would be a good idea to turn the user_id + information combo in the table unique. As so, everytime a user tried to save new information it would only save the one information I already didn't have. So, the first query being
INSERT INTO table VALUES ("1","cake"),("1","pie"),("1","bedsheets")
And as the user logins a second time and it being
INSERT INTO table VALUES ("1","cake"),("1","pie"),("1","bedsheets"),("1","chocolate")
It would only save ("1","chocolate") because (id,info) being an unique pair all other would not be inserted. I came upon the realization they all fail if only one fails. So my question is: is there any way to override this operation? Or do I have to query the db first to filter the information I already have? tyvm...
When you use the IGNORE Keyword, so every errors, in the execution are ignored. Example: if you have a duplicate or PRIMARY key error while executing a INSERT Statement, so it will ignored and the execution is not aborted
Use this:
I NSERT IGNORE INTO table VALUES ("1","cake"),("1","pie"),("1","bedsheets"),("1","chocolate");
I'm trying to create a code for a single button where it will perform either of two actions where it will add to the database if the user currently don't have the record while it will update the user's record if the user has records already. I've done it like this:
if() {
mysql_query("INSERT INTO table...");
}
else {
mysql_query("UPDATE table SET...");
}
Is it possible?
Yes, what you've written will work. If you have a way to know if there already exists a row or not without making an additional query just for this bit of code, then do exactly as you wrote.
If, however, you planned to first SELECT from the table to see if a row exists, then conditionally INSERT or UPDATE, you will perform more queries than necessary.
It would be better to either:
Have a PRIMARY KEY or other constraint on the table prevent duplicate INSERTs. Then issue an INSERT ... ON DUPLICATE KEY UPDATE query. This will attempt to INSERT the row, and if it is a duplicate, automatically perform the specified UPDATE to that row instead.
Issue the UPDATE query and check mysql_affected_rows to see if it updated an existing row. If not, then issue the INSERT query to create the new row.
Which one is more appropriate depends on your application.
you can use INSERT ... ON DUPLICATE KEY UPDATE Syntax like:
INSERT INTO table (a,b,c) VALUES (1,2,3)
ON DUPLICATE KEY UPDATE c=c+1;
http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html
If you have properly set unique keys, you should use REPLACE so you could remove the if.
REPLACE INTO table VALUE (...);
Pay attention that this is a MySQL extension, thus not portable to other DBs.
Yes, you could try the insert then if it fails try the update.
But you could use the MYSQL sql "REPLACE" keyword, which will insert a new record if it doesn't exist or delete the existing record and insert your new one if it does.
You could also use the INSERT ... ON DUPLICATE KEY UPDATE syntax
(explained here - Link to MYSQL ref which seems to be the closest fit to your requirement.
yes it is possible
first write a query for check that record is already exist or not.
Yes it is possible , it will work
I have two INSERT commands, that are useless to me like that because the two sets of rows - the ones that are already in the table, and the ones I have as INSERT commands - are not disjunct. Both commands insert lots of rows, and lots of values.
Therefore I get the duplicate entry error if I want to execute those lines.
Is there any easy way to 'convert' those commands into UPDATE?
I know this sounds stupid, because why do I make INSERT commands, if I want to UPDATE. Just to make it a clear scenario: another developer gave me the script:)
Thanks in advance,
Daniel
EDIT - problem solved
First I created a table and filled it up with my INSERT commands, then I used the following REPLACE command:
REPLACE
INTO table_1
SELECT *
FROM table_2;
This can originally be found at: How can I merge two MySQL tables?
MySQL's REPLACE keyword does this. Simply replace the INSERT keyword in your queries with the word REPLACE and it should update the rows instead of inserting new ones. Please note that it will only work if you're inserting a primary key or unique key column.
You would have to rewrite them to updates by hand. If I encouter such a problem, I query for the count of certain primary key first, if none is found I insert a generic dataset and update it afterwards. By this, new data can be added and already existing data will be updated, and you don't have to differentiate between inserting new data and updating data.
For MySQL, you can use either the INSERT IGNORE or the INSERT ... ON DUPLICATE UPDATE syntaxes. See the MySQL reference manual
You can easily modify your queries to update duplicate rows, see INSERT ... ON DUPLICATE KEY syntax in MySQL
If you got 100 000 users, is MySQL executing one SQL query at the time?
Because in my PHP code I check if a certain row exists; if it doesn't it creates one. If it does, it just updates the row counter.
It crossed my mind that perhaps 100 users are checking if the row exists at the same time, and when it doesn't they all create one row each.
If MySQL is handling them sequentially I know that it won't be an issue, then one user will check if it exists, if not, create it. The other user will check if it exists, and since that's the case, it just updates the counter.
But if they all check if it exists at the same time and let's say it doesn't, then they all create one row and the whole table structure will fail.
Would be great if someone could shed some light on this topic.
Use a UNIQUE constraint or, if viable, make the primary key one of your data items and the SQL server will prevent duplicate rows from being created. You can even use the "ON DUPLICATE KEY UPDATE ..." syntax to specify the alternate operation if the row already exists.
From your comments, it sounds like you could use the user_id as your primary key, in which case, you'd be able to use something like this:
INSERT INTO usercounts (user_id,usercount)
VALUES (id-goes-here,1)
ON DUPLICATE KEY UPDATE usercount=usercount+1;
If you put the check and insert into a transaction then you can avoid this problem. This way, the check and create will be run as one one query and there shouldn't be any confusion