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• mailing system DB structure, need help

  - by Anna

  i have a system there user(sender) can write a note to friends(receivers), number of receivers=0. Text of the message is saved in DB and visible to sender and all receivers then they login to system. Sender can add more receivers at any time. More over any of receivers can edit the message and even remove it from DB. For this system i created 3 tables, shortly: users(userID, username, password) messages(messageID, text) list(id, senderID, receiverID, messageID) in table "list" each row corresponds to pair sender-receiver, like sender_x_ID -- receiver_1_ID -- message_1_ID sender_x_ID -- receiver_2_ID -- message_1_ID sender_x_ID -- receiver_3_ID -- message_1_ID Now the problem is: 1. if user deletes the message from table "messages" how to automatically delete all rows from table "list" which correspond to deleted message. Do i have to include some foreign keys? More important: 2. if sender has let say 3 receivers for his message1 (username1, username2 and username3) and at certain moment decides to add username4 and username5 and at the same time exclude username1 from the list of receivers. PHP code will get the new list of receivers (username2, username3, username4, username5) That means insert to table "list" sender_x_ID -- receiver_4_ID -- message_1_ID sender_x_ID -- receiver_5_ID -- message_1_ID and also delete from table "list" the row corresponding to user1 (which is not in the list or receivers any more) sender_x_ID -- receiver_1_ID -- message_1_ID which sql query to send from PHP to make it in an easy and intelligent way? Please help! Examples of sql queries would be perfect!

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• Does the MySQLdb module support prepared statements ?

  - by planetp

  Does MySQLdb support server-side prepared statements? I can't figure this out from its manual.

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• group by, order by, with join

  - by Scarface

  Hey guys, quick question, I have this query, and I am trying to get the latest comment for each topic and then sort those results in descending order (therefore one comment per topic). I have what I think should work, but my join always messes my results up. Somehow, it seems to have sorted the end results properly, but has not taken the latest comment from each topic instead it seems to have just taken a random comment. If anyone has any ideas, would really appreciate any advice SELECT * FROM comments JOIN topic ON topic.topic_id=comments.topic_id WHERE topic.creator='admin' GROUP BY comments.topic_id ORDER BY comments.time DESC table comments is structured like id time user message topic_id table topic is structured like topic_id subject_id topic_title creator timestamp description

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• Combining the value of GetLastError and a custom error message

  - by Jessica

  I have a function that returns a different DWORD value for each case there is an error. So I have the following defines: #define ERR_NO_DB_CONNECTION 0x90000 #define ERR_DB_NOT_OPEN 0x90001 #define ERR_DB_LOCKED 0x90002 #define ERR_DB_CONN_LOST 0x90003 Now, I return those values when an error occurs. I need to also return the value of GetLastError in the same return. No, I can't read it later. I tried combining it different ways, eg: return ERR_DB_NOT_OPEN + GetLastError(); and then extract the error by subtracting the value of ERR_DB_NOT_OPEN but since I need to use this in functions where there can be several return values it can get quite complex to do that. Is there any way to achieve this? I mean, combine the value + GetLastError and extract them later? Code is appreciated. Thanks Jess.

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• INSERT..ON DUPLICATE KEY UPDATE - but NOT using the duplicate key to compare.

  - by calumbrodie

  I am trying to solve a problem I have inherited with poor treatment of different data sources. I have a user table that contains BOTH good and evil users. create table `users`( `user_id` int(13) NOT NULL AUTO_INCREMENT , `email` varchar(255) , `name` varchar(255) , PRIMARY KEY (`user_id`) ); In this table the primary key is currently set to be user_id. I have another table ('users_evil') which contains ONLY the evil users (all the users from this table are included in the first table) - the user_id's on this table do NOT correspond to those in the first table. I want to have all my users in one table, and simply flag which are good and which are evil. What I want to do is alter the user table and add a column ('evil') which defaults to 0. I then want to dump the data from my 'users_evil') table and then run an INSERT..ON DUPLICATE KEY UPDATE with this data into the first table (setting 'evil'=1 where the emails match) The problem is that the 'PK' is set to the user_id and not the 'email'. Any suggestions, or even another strategy to successfully achive this. Can I run this statement but treat another column as PK only for the duration of the statement.

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• (database design):Which tables should be created for all kindes files (images, attached email files,

  - by meyosef

  Hi, I new in database design: I have question with my own few solution,what do you thinks?: Which tables should be created for all kinds files (images, attached email files,text files for store email body, etc..) that stored in my online store? *option 1:use seperate table for files types * files{ id files_types_id FK file_path file_extension } files_types{ id type_name (unique) } *option 2: use bool field for each file type * files{ id file_path file_extension is_image_main is_image_icon is_image_logo is_pdf_file is_text_file } **option 3: use 1 enum field 'file_type' for each file type ** files{ id file_path file_extension file_type (image_main,image_icon,image_logo,image_main,pdf,text) **enum** } Thanks you, Yosef

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• Increment my id in my insert request

  - by Mercer

  hello, i have a table with some rows. idClient, name, adress,country,... i want to know how i can do an insert into this table with auto increment my idClient in my sql request..? Thx. edit: i want do a request like this insert into Client values((select max(idClient),...)

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• How to verify if two tables have exactly the same data?

  - by SiLent SoNG

  Basically we have one table (original table) and it is backed up into another table (backup table); thus the two tables have exactly the same schema. At the beginning both tables (original table and backup table) contains exactly the same set of data. After sometime for some reason I need to verify whether dataset in the original table has changed or not. In order to do this I have to compare the dataset in the original table against the backup table. Let's say the original table has the following schema: `create table LemmasMapping ( lemma1 int, lemma2 int, index ix_lemma1 using btree (lemma1), index ix_lemma2 using btree (lemma2) )` How could I achieve the dataset comparision? Update: the table does not have a primary key. It simply stores mappings between two ids.

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• What is the best way to go about grouping rows by the same timestamp?

  - by Luke

  Hello all. I am looking for some advice. I have rows of data in the database that i want to group together. There is a timestamp involved. That column is called date. What is the best way to go about grouping rows by the same timestamp. EDITED..... <? $result = mysql_query("SELECT * FROM ".TBL_FIXTURES." ORDER BY date"); $current_week = null; while ($row = mysql_fetch_assoc($result)) { if ($row['date'] != $current_week) { $current_week = $row['date']; echo 'Week ' . $current_week .': '; } echo $row['home_user']; echo $row['home_team']; echo $row['away_user']; echo $row['away_team']; } ?> I have this code. What i am trying to do is organise each round of fixtures in a row with a title Week 1 - date. I want Week 1 and the date and all fixtures with that date displayed. Then move onto week 2 and the date and all fixtures again. This should be done for every fixture in the database, so if there are 6 rounds of fixtures, there will be 6 dates and therefore 6 blocks of fixtures.. Please help, thanks

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• Stored Queries?

  - by phpeffedup

  Is it considered crazy to store common SQL queries for my web app in a database for use in execution? Or is that common practice? Or is it impossible? My thinking is, this way, I avoid hard-coding SQL into my application files, and add another level of abstraction. Is this crazy? Is this what a stored procedure is? Or is that something else?

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• C# Application process hangs after some time

  - by Chris

  Hi, I implemented a simple C# application which inserts about 350000 records into the database. This used to work well and the process took approximately 20 minutes. I created a progress bar which lets you know approximately the progress of the records insertion. When the progress bar reaches about 75% it stops progressing. I have to manually terminate the program as the process doesn't seem to complete. If I use less data (like 10000), the progress bar finishes and the process is completed. However when I try to insert all the records, this won't happen any more. Note that if I wait longer to terminate the program manually, more records would have been inserted. For example, if I terminate the program after 15 minutes, 200000 records are inserted, whereas if I terminate the program after 20 minutes, 250000 records are inserted. This program is using a single thread. In face I can't do anything else until the process is complete. Does this have anything to do with threading or processes? Any feedback will be greatly appreciated. Thanks.

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• With modern social networking and scaling, can Cassandra replace the standard relational database su

  - by alex

  Is it possible to build the entire social networking application on cassandra? Sure, it takes longer to set up, but it scales much better. Correct? Please list the situations when Cassandra should be used.

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• SELECT set of most recent id, amount FROM table, where id occurs many times

  - by Jon Cram

  I have a table recording the amount of data transferred by a given service on a given date. One record is entered daily for a given service. I'd like to be able to retrieve the most recent amount for a set of services. Example data set: serviceId | amount | date ------------------------------- 1 | 8 | 2010-04-12 2 | 11 | 2010-04-12 2 | 14 | 2010-04-11 3 | 9 | 2010-04-11 1 | 6 | 2010-04-10 2 | 5 | 2010-04-10 3 | 22 | 2010-04-10 4 | 17 | 2010-04-19 Desired response (service ids 1,2,3): serviceId | amount | date ------------------------------- 1 | 8 | 2010-04-12 2 | 11 | 2010-04-12 3 | 9 | 2010-04-11 Desired response (service ids 2, 4): serviceId | amount | date ------------------------------- 2 | 11 | 2010-04-12 4 | 17 | 2010-04-19 This retrieves the equivalent as running the following once per serviceId: SELECT serviceId, amount, date FROM table WHERE serviceId = <given serviceId> ORDER BY date DESC LIMIT 0,1 I understand how I can retrieve the data I want in X queries. I'm interested to see how I can retrieve the same data using either a single query or at the very least less than X queries. I'm very interested to see what might be the most efficient approach. The table currently contains 28809 records. I appreciate that there are other questions that cover selecting the most recent set of records. I have examined three such questions but have been unable to apply the solutions to my problem.

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• What causes Python "Interpreter not Initialized" error?

  - by ?????

  I'm now on my third full day this week of trying to get OpenCV to work with Python. (I have been trying on and off for the past 6 months). I get this error Python 2.7.1 (r271:86882M, Nov 30 2010, 10:35:34) [GCC 4.2.1 (Apple Inc. build 5664)] on darwin Type "help", "copyright", "credits" or "license" for more information. dlopen("/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/readline.so", 2); import readline # dynamically loaded from /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/readline.so >>> import cv dlopen("./cv.so", 2); Fatal Python error: Interpreter not initialized (version mismatch?) and then it crashes (core dumps). python -v gives nothing after the dlopen. Any ideas from anyone who actually knows about this error?

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• Keeping video viewing statistics breakdown by video time in a database

  - by Septagram

  I need to keep a number of statistics about the videos being watched, and one of them is what parts of the video are being watched most. The design I came up with is to split the video into 256 intervals and keep the floating-point number of views for each of them. I receive the data as a number of intervals the user watched continuously. The problem is how to store them. There are two solutions I see. Row per every video segment Let's have a database table like this: CREATE TABLE `video_heatmap` ( `id` int(11) NOT NULL AUTO_INCREMENT, `video_id` int(11) NOT NULL, `position` tinyint(3) unsigned NOT NULL, `views` float NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `idx_lookup` (`video_id`,`position`) ) ENGINE=MyISAM Then, whenever we have to process a number of views, make sure there are the respective database rows and add appropriate values to the views column. I found out it's a lot faster if the existence of rows is taken care of first (SELECT COUNT(*) of rows for a given video and INSERT IGNORE if they are lacking), and then a number of update queries is used like this: UPDATE video_heatmap SET views = views + ? WHERE video_id = ? AND position >= ? AND position < ? This seems, however, a little bloated. The other solution I came up with is Row per video, update in transactions A table will look (sort of) like this: CREATE TABLE video ( id INT NOT NULL AUTO_INCREMENT, heatmap BINARY (4 * 256) NOT NULL, ... ) ENGINE=InnoDB Then, upon every time a view needs to be stored, it will be done in a transaction with consistent snapshot, in a sequence like this: If the video doesn't exist in the database, it is created. A row is retrieved, heatmap, an array of floats stored in the binary form, is converted into a form more friendly for processing (in PHP). Values in the array are increased appropriately and the array is converted back. Row is changed via UPDATE query. So far the advantages can be summed up like this: First approach Stores data as floats, not as some magical binary array. Doesn't require transaction support, so doesn't require InnoDB, and we're using MyISAM for everything at the moment, so there won't be any need to mix storage engines. (only applies in my specific situation) Doesn't require a transaction WITH CONSISTENT SNAPSHOT. I don't know what are the performance penalties of those. I already implemented it and it works. (only applies in my specific situation) Second approach Is using a lot less storage space (the first approach is storing video ID 256 times and stores position for every segment of the video, not to mention primary key). Should scale better, because of InnoDB's per-row locking as opposed to MyISAM's table locking. Might generally work faster because there are a lot less requests being made. Easier to implement in code (although the other one is already implemented). So, what should I do? If it wasn't for the rest of our system using MyISAM consistently, I'd go with the second approach, but currently I'm leaning to the first one. But maybe there are some reasons to favour one approach or another?

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• SQL: count days in date range?

  - by John Isaacks

  I have a query like this: SELECT COUNT(*) AS amount FROM daily_individual_tracking WHERE sales = 'YES' AND daily_individual_tracking_date BETWEEN '2010-01-01' AND '2010-03-31' I am selected from a date range. Is there a way to also get the total days in the date range?

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• Store database, good pattern for simultaneous access

  - by dygi

  I am kinda new to database designing so i ask for some advices or some kind of a good pattern. The situation is that, there is one database, few tables and many users. How should i design the database, or / and which types of queries should i use, to make it work, if users can interact with the database simultaneously? I mean, they have access to and can change the same set of data. I was thinking about transactions, but I am not sure, if that is the right / good / the only solution. I will appreciate some google keywords too.

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• Hibernate/Spring: getHibernateTemplate().save(...) Freezes/Hangs

  - by ashes999

  I'm using Hibernate and Spring with the DAO pattern (all Hibernate dependencies in a *DAO.java class). I have nine unit tests (JUnit) which create some business objects, save them, and perform operations on them; the objects are in a hash (so I'm reusing the same objects all the time). My JUnit setup method calls my DAO.deleteAllObjects() method which calls getSession().createSQLQuery("DELETE FROM <tablename>").executeUpdate() for my business object table (just one). One of my unit tests (#8/9) freezes. I presumed it was a database deadlock, because the Hibernate log file shows my delete statement last. However, debugging showed that it's simply HibernateTemplate.save(someObject) that's freezing. (Eclipse shows that it's freezing on HibernateTemplate.save(Object), line 694.) Also interesting to note is that running this test by itself (not in the suite of 9 tests) doesn't cause any problems. How on earth do I troubleshoot and fix this? Also, I'm using @Entity annotations, if that matters. Edit: I removed reuse of my business objects (use unique objects in every method) -- didn't make a difference (still freezes). Edit: This started trickling into other tests, too (can't run more than one test class without getting something freezing) Transaction configuration: <bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <property name="dataSource" ref="dataSource" /> </bean> <tx:advice id="txAdvice" transaction-manager="txManager"> <!-- the transactional semantics... --> <tx:attributes> <!-- all methods starting with 'get' are read-only --> <tx:method name="get*" read-only="true" /> <tx:method name="find*" read-only="true" /> <!-- other methods use the default transaction settings (see below) --> <tx:method name="*" /> </tx:attributes> </tx:advice> <!-- my bean which is exhibiting the hanging behavior --> <aop:config> <aop:pointcut id="beanNameHere" expression="execution(* com.blah.blah.IMyDAO.*(..))" /> <aop:advisor advice-ref="txAdvice" pointcut-ref="beanNameHere" /> </aop:config>

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• Checking if user owns file before deleting it

  - by Martin Hoe

  I'm building an API for my site that allows users to delete the files they upload. Obviously, I want to check if the user owns that file before they delete it through the API. I have a files table and a users table, here's the schema: f_id, s_id, u_id, name, size, uploaded u_id, username, password, email, activated, activation_code u_id is a foreign key. The u_id field in the files table points to the u_id in the users table. Given the users username, I want to find the users u_id, and then check if they own the file through the file ID (f_id). I wrote this SQL: $sql = 'SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f_id = ? AND u.u_id = ? LIMIT 1'; I'm assuming that'd work if I was given the users u_id in the API request, but alas I'm given only their username. How can I modify that SQL to find their user ID and use that? Thanks. Edit: Alright I've got this query but it's always returning an empty result set even though both the file ID and username exist. SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f.f_id = ? AND u.username = ? LIMIT 1

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• Store LAST_INSERT_ID() in a transaction

  - by Oden

  Hi, I use codeigniter's database abstarction, and im doing a transaction with it. My problem is, that i have several inserts into several tables, but i need the insert id from the first insert query. Is there any way to store the last insert id for more than one following insert?

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• SQL query for fetching friend list

  - by Bhavyanshu

  I need help with SQL query. I have two tables. One is users and other one is userfriends users table: aid email firstname 1 [email protected] example 2 [email protected] example2 3 [email protected] example3 4 [email protected] example4 userfriends tables: reqid email friendemail status 1 [email protected] [email protected] 1 (example1 is frnds with example2) 2 [email protected] [email protected] 2 (example2 request pending) 3 [email protected] [email protected] 1 (example1 is frnds with example3) 4 [email protected] [email protected] 1 (example1 is frnds with example4) So when status is 2 the add request is pending and at status 1 they are friends. What i want is that i want to retrieve the complete friendlist for user example1. I want to pull out names from users table for corresponding output from previous query to display as friendlist.

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• How i can do the following querry to get needed information

  - by Night Walker

  Hello there I have two tables CompList table with following columns : CompId , McID , station , slot ,subslot , and several others BookingTable with columns: CompId , LineID , McID , station , slot ,subslot. I want to get following result: rows only that CompList.CompId == BookingTable.CompId (only CompId that is in both tables) and i need in the result columns from CompList: CompId , McID , station , slot ,subslot . and from BookingTable: LineID , McID , station , slot ,subslot and how i will be able to distinguish between same columns with same table in the result table them in the result table? Thanks for help.

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• Getting all database entries into organized array

  - by Industrial

  Hi everyone, I have just made the update/add/delete part for the "Closure table" way of organizing query hierarchical data that are shown on page 70 in this slideshare: http://www.slideshare.net/billkarwin/sql-antipatterns-strike-back However, I have a bit of an issue getting the full tree back as an multidimensional array from a single query. Here's what I would like to get back: array ( 'topvalue' = array ( 'Subvalue', 'Subvalue2', 'Subvalue3' = array ('Subvalue 1', 'Subvalue 2', 'Subvalue 3' ) ); );

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• How do I set ORDER BY params using prepared PDO statement?

  - by Marlorn

  I'm having problems using params in the ORDER BY section of my SQL. It doesn't issue any warnings, but prints out nothing. $order = 'columnName'; $direction = 'ASC'; $stmt = $db->prepare("SELECT field from table WHERE column = :my_param ORDER BY :order :direction"); $stmt->bindParam(':my_param', $is_live, PDO::PARAM_STR); $stmt->bindParam(':order', $order, PDO::PARAM_STR); $stmt->bindParam(':direction', $direction, PDO::PARAM_STR); $stmt->execute(); The :my_param works, but not :order or :direction. Is it not being internally escaped correctly? Am I stuck inserting it directly in the SQL? Like so: $order = 'columnName'; $direction = 'ASC'; $stmt = $db->prepare("SELECT * from table WHERE is_live = :is_live ORDER BY $order $direction"); Is there a PDO::PARAM_COLUMN_NAME constant or some equivalent? Thanks!

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• PHP export to text file - Only saving first line.

  - by wertz8090

  I'm trying to export some extracted $_POST information into a text file, however my code is only capturing the first variable and ignoring the rest. I'm saving the information to the text file in this manner: $values = "First Name: $fName\r\n"; $values .= "Last Name: $lName\r\n"; $values .= "Address: $address\r\n"; etc. This is the code I use to write to the text file: $fp = @fopen("person.data", "w") or die("Couldn't open person.data for writing!"); $numBytes = @fwrite($fp, $values) or die("Couldn't write values to file!"); @fclose($fp); Any ideas on why it would only save the first $values ($fName) variable but not the rest of them? It actually saves the first part of the $values string for all of them (so I see Last Name:, Address:, etc. on separate lines in the text file) but the called variables $lName and $address do not appear.

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