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  • Can I join between two MySQL tables stores on separate machines?

    - by CuriousCoder
    I have a relatively light query that needs information from a local MySQL table along with another MySQL table which is stored on a physically separate machine (on the same network). I'm keen to avoid setting up replication just to facilitate this light query that only needs executed once a day. Is there any way that I can join with a table on a remote machine using one query? Or run a SELECT INTO into a local table. Notes I'm using C# & .NET 4.

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  • With PHP and AJAX, Can two clients inter-exchange data without MySQL?

    - by Devyn
    Hi, Let's assume I'm developing a AJAX, PHP chess game. During the game, one movement of a player will be notified to the another but we are not saving that information. Normally, we used to store in MySQL every time a player makes movement and show update position to another player. What I want is to reduce MySQL load as much as possible and server is not interested in movements between two players. Server will only save final result like who wins. So what should I do?

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  • Can MySQL reasonably perform queries on billions of rows?

    - by haxney
    I am planning on storing scans from a mass spectrometer in a MySQL database and would like to know whether storing and analyzing this amount of data is remotely feasible. I know performance varies wildly depending on the environment, but I'm looking for the rough order of magnitude: will queries take 5 days or 5 milliseconds? Input format Each input file contains a single run of the spectrometer; each run is comprised of a set of scans, and each scan has an ordered array of datapoints. There is a bit of metadata, but the majority of the file is comprised of arrays 32- or 64-bit ints or floats. Host system |----------------+-------------------------------| | OS | Windows 2008 64-bit | | MySQL version | 5.5.24 (x86_64) | | CPU | 2x Xeon E5420 (8 cores total) | | RAM | 8GB | | SSD filesystem | 500 GiB | | HDD RAID | 12 TiB | |----------------+-------------------------------| There are some other services running on the server using negligible processor time. File statistics |------------------+--------------| | number of files | ~16,000 | | total size | 1.3 TiB | | min size | 0 bytes | | max size | 12 GiB | | mean | 800 MiB | | median | 500 MiB | | total datapoints | ~200 billion | |------------------+--------------| The total number of datapoints is a very rough estimate. Proposed schema I'm planning on doing things "right" (i.e. normalizing the data like crazy) and so would have a runs table, a spectra table with a foreign key to runs, and a datapoints table with a foreign key to spectra. The 200 Billion datapoint question I am going to be analyzing across multiple spectra and possibly even multiple runs, resulting in queries which could touch millions of rows. Assuming I index everything properly (which is a topic for another question) and am not trying to shuffle hundreds of MiB across the network, is it remotely plausible for MySQL to handle this? UPDATE: additional info The scan data will be coming from files in the XML-based mzML format. The meat of this format is in the <binaryDataArrayList> elements where the data is stored. Each scan produces = 2 <binaryDataArray> elements which, taken together, form a 2-dimensional (or more) array of the form [[123.456, 234.567, ...], ...]. These data are write-once, so update performance and transaction safety are not concerns. My naïve plan for a database schema is: runs table | column name | type | |-------------+-------------| | id | PRIMARY KEY | | start_time | TIMESTAMP | | name | VARCHAR | |-------------+-------------| spectra table | column name | type | |----------------+-------------| | id | PRIMARY KEY | | name | VARCHAR | | index | INT | | spectrum_type | INT | | representation | INT | | run_id | FOREIGN KEY | |----------------+-------------| datapoints table | column name | type | |-------------+-------------| | id | PRIMARY KEY | | spectrum_id | FOREIGN KEY | | mz | DOUBLE | | num_counts | DOUBLE | | index | INT | |-------------+-------------| Is this reasonable?

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  • C#+Mysql Runs out of Connections. I am using 'using' and closing all connections immediately.

    - by Cyril Gupta
    In the application that I am making right now, I am getting this error: error connecting: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached. Evidently I am touching max-count in the connection pool. I am dutifully using 'using' with all connection objects and freeing them up immediately when the function is done with them. This is on C#, and I am using the MySql Data Dll. Is there something wrong with the dotnet connector for MySql? Is there a workaround?

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  • Can I use a single MySQL query to select distinct rows and then non-distinct rows if a limit hasn't

    - by Matt Rix
    I hope I'm explaining this properly, my knowledge of MySQL is quite limited. Let's say I have a table with rows that have name and shape fields. I'd like to select a bunch of rows from a table, but return all of the rows with unique shape field values first. If I have less than a certain number of rows, let's say 7, then I'd like to fill the remaining result rows with non-unique shape rows. The best way I can word it is that they're "ordered by uniqueness, and then by some other value". So, I don't want: square, square, circle, circle, rectangle, square, triangle I'd like to have: square, circle, rectangle, triangle, square, square, circle Is this possible to do using a single SQL query? I'm using MySQL with PHP, if that makes any difference. Thanks!

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  • pitfalls with mixing storage engines in mysql with django?

    - by Dave Orr
    I'm running a django system over mysql in amazon's cloud, and the database default is innodb. But now I want to put a fulltext index on a couple of tables for searching, which evidently requires myisam. The obvious solution is to just tell mysql to ALTER TABLE to myisam, but are there going to be any issues with that? One that comes to mind is that I'll have to remember to do that any time I build a new version of the database, which should theoretically be rare, but there doesn't seem to be a way to tell django to please set the storage engine at the table level. I guess I could write a migration (we use south). Any other things I might be missing? What could possibly go wrong?

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  • Reading data from a MySQL database into a HTML Table?

    - by Michael McKay
    So i am working on a project and need some advice. I have a MySQL database that stores events, i know how to code this functionality in PHP but im just stuck of a few specifics. As the project that I am creating is a timetable, the most important attributes are the day of the event, starting time and finishing time. Once i have read this data from the MYSQL database using my PHP script, how do i go about inserting these events in to a html timetable? Lets say i have record like below in my events table: Event ID = 01 Event Day = Monday Event Start = 12:00 Event End = 14:00 How would I then put that into a html table, bearing in mind that i may have mutiple events for a day?

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  • Best way to have unique key over 500M varchar(255) records in mysql/innodb?

    - by taw
    I have url column with unique key over it - but its performance on updates is absolutely atrocious. I suspect that's because the index doesn't all fit in memory. So I was thinking, how about adding a column of md5(url) with 16 bytes of binary data and unique-keying that instead. What would be the best datatype for that? I'd love to be able to just see 32-character hex hash, while mysql would convert it to/from 16 binary bytes and index that, as programs using the database might have some troubles with arbitrary binary data that I'd rather avoid if possible (also I'm a bit afraid that mysql might get some strange ideas about character sets and for example overalocating storage for that by 3:1 because it thinks it might need utf8, how do I avoid that for cure?).

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  • MYSQL - Adding result set A to result set B? Please see my example

    - by BlackberryFan
    I have two mysql tables. They are laid out in this manner: user_info id | emailContact _______________________ 1 | [email protected] 3 | [email protected] user_biz_info id | emailContact _________________________ 8 | [email protected] 9 | [email protected] What kind of join would I use to create a result set of information like this: id | emailContact ________________________________ 1 - [email protected] 3 - [email protected] 8 - [email protected] 9 - [email protected] I have tried the following: SELECT p.id, p.emailContact, b.id, b.emailContact FROM user_info p, user_business_info b But it seems that this is an incorrect approach. Would someone be able to suggest the correct approach in this or possibly point me in the direction of some tutorials that cover this type of mysql join, as this is what I assume is needed in this case. Thanks for your time in reading through my question!!

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  • is there a limit of merge tables with Mysql ?

    - by sysko
    I'm working on a database with mysql 5.0 for an open source project it's used to stored sentences in specific languages and their translations in other languages I used to have a big table "sentences" and "sentences_translations" (use to join sentences to sentences) table but has we have now near one million entries, this begin to be a bit slow, moreover, most of request are made using a "where lang =" so I've decided to create a table by language sentences_LANGUAGECODE and sentences_translation_LANGSOURCE_LANGTARGET and to create merge table like this sentences_ENG_OTHERS which merge sentences_ENG_ARA sentences_ENG_DEU etc... when we want to have the translations in all languages of an english sentence sentences_OTHERS_ENG when we want to have only the english translations of some sentences I've created a script to create all these tables (they're around 31 languages so more than 60 merge table), I've tested, that works really great a request which use to take 160ms now take only 30 :) but I discover that all my merge table after the 15th use to have "NULL" as type of storage engine instead of MRG_MYISAM, and if delete one, then I can create an others, using FLUSH table between each creation also allow me to create more merge tables so is this a limitation from mysql ? can we override it ? thanks for your answers

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  • Do I need the text "_size" in the my.cnf file for mysql 5.1?

    - by chongman
    This is a pretty simple question about setting parameters in the my.cnf file for mysql 5.1. This page gives me the parameters I can tune: http://dev.mysql.com/doc/refman/5.0/en/server-parameters.html and so I think I would need to write key_buffer_size = 256M But when I open my current my.cnf, it has the line: key_buffer = 16M My question is, do I need "key_buffer_size" or "key_buffer" or does it not matter which I use? And, how would I know if something in the my.cnf is incorrect? Where's the daemon start log file? I am running ubuntu; I think version 8.04 LTS

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  • Can MySQL automatically specify `_utf8` for inserts to UTF-8 columns?

    - by Neil
    I have a table like this, where one column is latin1, the other is UTF-8: Create Table: CREATE TABLE `names` ( `name_english` varchar(255) character NOT NULL, `name_chinese` varchar(255) character set utf8 default NULL, ) ENGINE=MyISAM DEFAULT CHARSET=latin1 When I do an insert, I have to type _utf8 before values being inserted into UTF-8 columns: insert into names (name_english = "hooey", name_chinese = _utf8 "??"); However, since MySQL should know that name_chinese is a UTF-8 column, it should be able to know to use _utf8 automatically. Is there any way to tell MySQL to use _utf8 automatically, so when I'm programatically making prepared statements, I don't have to worry about including it with the right parameters?

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  • How to insert large files in mysql database using php? [closed]

    - by anjan
    Hi! I want to upload a large file of size 10M max to my mysql database. Using .htaccess i changed the PHP's own file upload limit to "10485760" = 10M, i am able to upload files upto 10M size without any problem. But i can not insert the file in database if it is more that 1M in size. i am using file_get_contents to read all file data and pass it to the insert query as a string to be inserted into a LONGBLOB field. But files with more than 1M size is not being added to database, though i can use print_r($_FILES) to examine that the file uploaded correctly. Any help will be appreciated and i will need it within next 6 hours. So, please help! best regards, Anjan * This is a duplicate of http://stackoverflow.com/questions/492549/how-can-i-insert-large-files-in-mysql-db-using-php *

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