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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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  • SQL query - choosing 'last updated' record in a group, better db design?

    - by Jimmy
    Hi, Let's say I have a MySQL database with 3 tables: table 1: Persons, with 1 column ID (int) table 2: Newsletters, with 1 column ID (int) table 3: Subscriptions, with columns Person_ID (int), Newsletter_ID (int), Subscribed (bool), Updated (Datetime) Subscriptions.Person_ID points to a Person, and Subscription.Newsletter_ID points to a Newsletter. Thus, each person may have 0 or more subscriptions to 0 or more magazines at once. The table Subscriptions will also store the entire history of each person's subscriptions to each newsletter. If a particular Person_ID-Newsletter_ID pair doesn't have a row in the Subscriptions table, then it's equivalent to that pair having a subscription status of 'false'. Here is a sample dataset Persons ID 1 2 3 Newsletters ID 4 5 6 Subscriptions Person_ID Newsletter_ID Subscribed Updated 2 4 true 2010-05-01 3 4 true 2010-05-01 3 5 true 2010-05-10 3 4 false 2010-05-15 Thus, as of 2010-05-16, Person 1 has no subscription, Person 2 has a subscription to Newsletter 4, and Person 3 has a subscription to Newsletter 5. Person 3 had a subscription to Newsletter 4 for a while, but not anymore. I'm trying to do 2 kinds of query. A query that shows everyone's active subscriptions as of query time (we can assume that updated will never be in the future -- thus, this means returning the record with the latest 'updated' value for each Person_ID-Newsletter_ID pair, as long as Subscribed is true (if the latest record for a Person_ID-Newsletter_ID pair has a Subscribed status of false, then I don't want that record returned)). A query that returns all active subscriptions for a specific newsletter - same qualification as in 1. regarding records with 'false' in the Subscribed column. I don't use SQL/databases often enough to tell if this design is good, or if the SQL queries needed would be slow on a database with, say, 1M records in the Subscriptions table. I was using the Visual query builder tool in Visual Studio 2010 but I can't even get the query to return the latest updated record for each Person_ID-Newsletter_ID pair. Is it possible to come up with SQL queries that don't involve using subqueries (presumably because they would become too slow with a larger data set)? If not, would it be a better design to have a separate Subscriptions_History table, and every time a subscription status for a Person_ID-Newsletter-ID pair is added to Subscriptions, any existing record for that pair is moved to Subscriptions_History (that way the Subscriptions table only ever contains the latest status update for any Person_ID-Newsletter_ID pair)? I'm using .net on Windows, so would it be easier (or the same, or harder) to do this kind of queries using Linq? Entity Framework? Thanks!

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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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  • 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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  • 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 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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  • 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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  • 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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  • 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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  • MySQL: Query to obtain recipes using all given ingredients.

    - by John_A
    hi I have the following simplified tables: CREATE TABLE recipe(id int, name varchar(25)); CREATE TABLE ingredient(name varchar(25)); CREATE TABLE uses_ingredient(recipe_id int, name varchar(25)); I want to make a query that returns all id's of recipes that contain both Chicken and Cream. I have tried SELECT recipe_id FROM uses_ingredient INNER JOIN (SELECT * FROM ingredient WHERE name="Chicken" OR name="Cream") USING (name) GROUP BY recipe_id HAVING COUNT(recipe_id) >= (SELECT COUNT(*) FROM theme); which gives me :"ERROR 1248 (42000): Every derived table must have its own alias" and is probably wrong too. Next I tried SELECT recipe_id FROM (SELECT * FROM ingredient WHERE name="Chicken" OR name="Cream") AS t INNER JOIN uses_ingredient USING (name) GROUP BY recipe_id HAVING COUNT(recipe_id)>= (SELECT COUNT(*) FROM t); which gives "ERROR 1146 (42S02): Table 'recipedb.t' doesn't exist" I want to avoid creating temporary tables including using ENGINE=MEMORY.

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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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