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  • Connect to a MySQL database and count the number of rows.

    - by Hugo
    Hi there! I need to connect to a MySQL database and then show the number of rows. This is what I've got so far; <?php include "connect.php"; db_connect(); $result = mysql_query("SELECT * FROM hacker"); $num_rows = mysql_num_rows($result); echo $num_rows; ?> When I use that code I end up with this error; Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in C:\Documents and Settings\username\Desktop\xammp\htdocs\news2\results.php on line 10 Thanks in advance :D

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  • SQL qn:- comparing data in rows

    - by rayhan
    hi, i would like to compare numeric data in rows. for eg, i have a table that has a column as such:- Number ====== 1.88 9.99 8.76 9.88 I want to compare 2nd value, 3rd value, 4th value to the 1st value. And then 3rd, 4th value to the 2nd. then 4th to 3rd. How can i construct an sql to do this?

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  • Zend Framework: How to download file from mySql Blob field.

    - by Awan
    I am uploading files(any type) in MySql tables's blob field. Now I am able to get binary data from that field and when I print it, it shows binary data in firbug console. But I want to download that file as it was uploaded. How can I convert this binary data into orignal file? How to do it in zend? Thanks

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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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  • Securing Coredata objects

    - by Abraham Durairaj
    I am working on an application which has got some sensitive information. I am aware that it would be difficult for a layman to hack into iphone to get the information. If I use SQLite directly I have something called SQLite Cipher to encrypt / encode the database. Is there anyway where I can have the same way of encrypting the coredata so it makes it hard for hackers to get into the data. Can someone shed some light on this? Thanks in Advance

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  • MySQL: How to pull information from multiple tables based on information in other tables?

    - by Greg
    Ok, I have 5 tables which I need to pull information from based on one variable. gameinfo id | name | platforminfoid gamerinfo id | name | contact | tag platforminfo id | name | abbreviation rosterinfo id | name | gameinfoid rosters id | gamerinfoid | rosterinfoid The 1 variable would be gamerinfo.id, which would then pull all relevant data from gamerinfo, which would pull all relevant data from rosters, which would pull all relevant data from rosterinfo, which would pull all relevant data from gameinfo, which would then pull all relevant data from platforminfo. Basically it breaks down like this: gamerinfo contains the gamers basic information. rosterinfo contains basic information about the rosters (ie name and the game the roster is aimed towards) rosters contains the actual link from the gamer to the different rosters (gamers can be on multiple rosters) gameinfo contains basic information about the games (ie name and platform) platform info contains information about the different platforms the games are played on (it is possible for a game to be played on multiple platforms) I am pretty new to SQL queries involving JOINs and UNIONs and such, usually I would just break it up into multiple queries but I thought there has to be a better way, so after looking around the net, I couldn't find (or maybe I just couldn't understand what I was looking at) what I was looking for. If anyone can point me in the right direction I would be most grateful.

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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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  • Core Data Change property value when another property changes

    - by user320587
    Hi, I have a Core Data Entity which has three properties startDate, endDate and duration. All three properties are persistent properties. I would like to know how I can calculate and update the duration property whenever the value for startDate and endDate changes? BTW, I won't be able to make the duration as transient property since I have to use the property for sorting in my table view? Any help is greatly appreciated Thanks, Javid

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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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  • Accelerometer data analysis

    - by jrrt
    Hello, I would like to know if there are some libraries/algorithms/techniques (python, if at all possible) that help to extract features from accelerometer data (extracted from and android phone, btw), like periodicity of movements, energy of acceleration and the like. Has anyone done this kind of task before? Thank you very much in advance :)

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  • how to load data and store the data from a file using numpy

    - by Charlie Epps
    I have the following file like this: 2 qid:1 1:0.32 2:0.50 3:0.78 4:0.02 10:0.90 5 qid:2 2:0.22 5:0.34 6:0.87 10:0.56 12:0.32 19:0.24 20:0.55 ... he structure is follwoing like that: output={} rel=2 qid=1 features={} # the feature list "1:0.32 2:0.50 3:0.78 4:0.02 10:0.90" output.append([rel,qid,features]) ... How can I write my python code to load the data, thanks

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  • How can I write a MySQL query to check multiple rows?

    - by Matt
    I have a MySQL table containing data on product features: feature_id feature_product_id feature_finder_id feature_text feature_status_yn 1 1 1 Webcam y 2 1 1 Speakers y 3 1 1 Bluray n I want to write a MySQL query that allows me to search for all products that have a 'y' feature_status_yn value for a given feature_product_id and return the feature_product_id. The aim is to use this as a search tool to allow me to filter results to product IDs only matching the requested feature set. A query of SELECT feature_id FROM product_features WHERE feature_finder_id = '1' AND feature_status_yn = 'y' will return all of the features of a given product. But how can I select all products (feature_product_id) that have a 'y' value when they are on separate lines? Multiple queries might be one way to do it, but I'm wondering whether there's a more elegant solution based purely in SQL.

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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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  • MySQL Simple query gives "Query was empty". Transaction help needed I think.

    - by user129609
    Hi, I'm trying to do a simple transaction in MySQL delimiter go start transaction; BEGIN DECLARE EXIT HANDLER FOR SQLEXCEPTION, SQLWARNING, NOT FOUND ROLLBACK; INSERT INTO jext_categories (Name) VALUES ('asdfas'); INSERT INTO jext_categories (Name) VALUES ('asdfas2'); END; commit; SELECT * FROM jext_categories; go delimiter ; but I keep getting an error saying query was empty. Could someone please tell me what I am doing wrong, and also, what is the proper format for doing a transaction in MySQL? Thanks!

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  • What's beyond c,c++ and data structure?

    - by sagacious
    I have learnt c and c++ programming languages.i have learnt data structure too. Now i'm confused what to do next?my aim is to be a good programmer. i want to go deeper into the field of programming and making the practical applications of what i have learnt. So,the question takes the form-what to do next?Or is there any site where i can see advantage of every language with it's features? sorry,if there's any language error and thanks in advance.

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  • Checking an empty Core Data relationship (SQLite)

    - by rwat
    I have a to-many relationship in my data model, and I'd like to get all the objects that have no corresponding objects in the relationship. For example: Customer - Purchases I want to get all Customers that have 0 Purchases. I've read somewhere that I could use "Purchases[SIZE] = 0", but this gives me an unsupported function expression error, which I think means it doesn't work with a SQLite backing store (which I don't want to switch from, due to some performance constraints). Any ideas?

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  • UIDatePicker Not storing time in core data

    - by Derek
    Hi, I am using a UIDatepicker with only "Time", I save the time in a NSDate object type, however when I try to store the Object in core data I get an error saying its not a NSDate type... *tt = [pickerTime date]; [myObject setValue:tt forKey:@"time"]; Thanks,

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