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  • Which collation should I use to store these country names in MySQL?

    - by morpheous
    I am trying to store a list of countries in a mySQL database. I am having problems storing (non English) names like these: São Tomé and Príncipe República de El Salvador They are stored with strange characters in the db, (and therefore output strangely in my HTML pages). I have tried using different combinations of collations for the database and the MySQL connection collation: The "obvious" setting was to use utf8_unicode_ci for both the databse and the connection information. To my utter surprise, that did not solve the problem. Does anyone know how to resolve this issue?

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  • SQL query: how to translate IN() into a JOIN?

    - by tangens
    I have a lot of SQL queries like this: SELECT o.Id, o.attrib1, o.attrib2 FROM table1 o WHERE o.Id IN ( SELECT DISTINCT Id FROM table1, table2, table3 WHERE ... ) These queries have to run on different database engines (MySql, Oracle, DB2, MS-Sql, Hypersonic), so I can only use common SQL syntax. Here I read, that with MySql the IN statement isn't optimized and it's really slow, so I want to switch this into a JOIN. I tried: SELECT o.Id, o.attrib1, o.attrib2 FROM table1 o, table2, table3 WHERE ... But this does not take into account the DISTINCT keyword. Question: How do I get rid of the duplicate rows using the JOIN approach?

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  • Does it make sense to use BOTH mongodb and mysql in the same rails application?

    - by Brian Armstrong
    I have a good reason to use mongodb for part of my app. But people generally describe it as not a good fit for "transactional" applications like a bank where transactions have to be exact/consistent, etc. Does it make sense to split the models up in Rails and have some of them use MySql and others mongo? Or will this generally cause more problems than it's worth? I'm not building a banking app or anything, but was thinking it might make sense for my users table or or transactions table (recording revenue) to do that part in MySql.

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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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  • 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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  • 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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  • 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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  • How to remove/hide <div></div> tags only without the content?

    - by candies
    For example I have: <div id ="test">[the content here]</div> The content within the div tags will appear after I called the id of div using ajax. This is the code: function dinamic(add) { var kode = add.value; if (!kode) return; xmlhttp2.open('get', '../template/get_id.php?kode='+kode, true); xmlhttp2.onreadystatechange = function() { if ((xmlhttp2.readyState == 4) && (xmlhttp2.status == 200)) { var add = document.getElementById("test"); add.innerHTML = xmlhttp2.responseText; } return false; } xmlhttp2.send(null); } So it will appear <div id="test">A</div> I'd like to put the content of div - A into mysql query. $test = $_GET['test']; $query = "select * from example where category='$test'"; I've tried to make variable $test of the div id to get the content but result of the query in category is none. I tried again, I put the div in to the query $query = "select * from example where category='<div id=\"test\">A</div>'"; Yes, It works. But when I did query on navicat, no results I got because there's spaces between A that is <div> and </div>. How to remove/hide the div tags only so its only appear the content? > $query = "select * from example where category='A'"; < Edit: If I echo the query on firefox browser will say "$query = "select * from example where category='[space]A[space]'";" And look at the bug(I use firebug), it will say "$query = "select * from example where category='<div id="test">A</div>'";" So my guessing why can't get result after query on navicat is there's spaces between A([space]A[space]), just have no idea how to remove/hide the div tags, I want to get this result only "$query = "select * from example where category='A'";" Thanks.

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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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  • Why would using a Temp table be faster than a nested query?

    - by Mongus Pong
    We are trying to optimise some of our queries. One query is doing the following: SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, INTO [#Gadget] FROM task t SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) as Client FROM [#Gadget] order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC DROP TABLE [#Gadget] (I have removed the complex subquery, cos I dont think its relevant other than to explain why this query has been done as a two stage process.) Now I would have thought it would be far more efficient to merge this down into a single query using subqueries as : SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) FROM ( SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, FROM task t ) as sub order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC This would give the optimiser better information to work out what was going on and avoid any temporary tables. It should be faster. But it turns out it is a lot slower. 8 seconds vs under 5 seconds. I cant work out why this would be the case as all my knowledge of databases imply that subqueries would always be faster than using temporary tables. Can anyone explain what could be going on!?!?

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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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  • how to compare two tables fields name with another value in mysql?

    - by I Like PHP
    I have two tables table_school school_open_time|school_close_time|school_day 8:00 AM | 9:00PM | Monday 10:00 AM | 7:00PM | Wednesday table_college college_open_time|college_close_time|college_day 10:00 AM | 8:00PM | Monday 10:00 AM | 9:00PM | Tuesday 10:00 AM | 5:00PM | Wednesday Now I want to select school_open_time school_close time, college_open_time and college_close_time according to today (means college_day=school_day=today), and also if there is no row for a specific day in any of one table then it display blank field ( LEFT JOIN , I think I can use). Please suggest me best and optimized query for this. UPDATE: if there is no open time and close time for school then college_open_time and college_close_time has to be returned( not to be filled in database,just return) as school_open_time and school_close_time. and there always must be college_open_time and college_close_time for a given day MORE UPDATE: i m using below query SELECT college_open_time,college_close_time ,school_open_time, school_close_time FROM tbl_college LEFT JOIN tbl_school ON school_owner_id=college_owner_id WHERE college_owner_id='".$_session['user_id']."' AND college_day='".date('l',time())."'"; it return single row (left hand having some value and right hand having blank value) when there is no row of a given day in table_school, BUT display seven rows with same value on left hand side(college_open_time, college_close_time) and 6 blank row on right hand side (school_open_time and school_close_time) i need only one row when both table have a row of a given day but using above query take only first row of corresponding table_school where school_owner_id is 50(let), it not see the condition that school_day name should be given day

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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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  • 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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  • 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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  • 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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