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  • Does introducing foreign keys to MySQL reduce performance

    - by Tam
    I'm building Ruby on Rails 2.3.5 app. By default, Ruby on Rails doesn't provide foreign key contraints so I have to do it manually. I was wondering if introducing foreign keys reduces query performance on the database side enough to make it not worth doing. Performance in this case is my first priority as I can check for data consistency with code. What is your recommendation in general? do you recommend using foreign keys? and how do you suggest I should measure this?

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  • MySQL join headaches, please help!

    - by Andrew Heath
    Ok, I've hit the wall here and need some help. Sample tables are as follows: SCENARIO_NATIONS [scenID] [side] [nation] scen001 1 Germany scen001 2 Britain scen001 2 Canada SCENARIO_NEEDUNITS [scenID] [unitID] scen001 0001 scen001 0003 scen001 0107 scen001 0258 scen001 0759 UNIT_BASIC_DATA [unitID] [nation] [name] 0001 Germany Mortars 0003 Germany Infantry 0107 Britain Lt 0258 Britain Infantry 0759 Canada Kilted Yaksmen Goal: given a scenID, pull a list of units from the database sorted by side, nation, name. I can do everything except for the side inclusion with: SELECT scenario_needunits.scenID, unit_basic_data.nation, unit_basic_data.name FROM scenario_needunits LEFT OUTER JOIN unit_basic_data ON scenario_needunits.unitID=unit_basic_data.unitID WHERE scenario_needunits.scenID='scen001' ORDER BY unit_basic_data.nation ASC, unit_basic_data.name ASC I've tried just dropping the SCENARIO_NATIONS table in as a LEFT OUTER JOIN on scenID but what ends up happening is that ALL units come back with a side of 1 because that's always the first side listed for the scenID in the SCENARIO_NATIONS table. Conceptually, what I think needs to happen is SCENARIO_NATIONS must be joined to both the scenID (to restrict it to just that scenario) and to each unit's nation but I don't have any idea how to do that and my Google-fu is inadequate. :-/

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  • how to avoid deadlock in mysql

    - by noam
    I have the following query (all tables are innoDB) INSERT INTO busy_machines(machine) SELECT machine FROM all_machines WHERE machine NOT IN (SELECT machine FROM busy_machines) and machine_name!='Main' LIMIT 1 Which causes a deadlock when I run it in threads, obviously because of the inner select, right? The error I get is: (1213, 'Deadlock found when trying to get lock; try restarting transaction') How can I avoid the deadlock? Is there a way to change to query to make it work, or do I need to do something else?

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  • php and mysql user tracking and reporting

    - by inertiahz
    Hi, I currently have a table which consists of user information and lesson id; the table layout looks like: ---------------------------------------------------- |employeeID|numVisits|lessonID1|lessonID2|lessonID3| ---------------------------------------------------- |33388 |2 |1 |0 |3 | and a lessons table which contains the information about the lesson: ------------------------------------------------------ |lessonID |cateogry |title |filepath |numberviews| ------------------------------------------------------ |1 |beginner |lesson |file:// |10 | Within the lessonID fields in the user table is an integer which tracks how many times someone has clicked on a lesson. Now what I am trying to do is in a report I have the top 5 people who have visited the site and would like to then be able to drill down into what lessons they have clicked on. Can anyone help with this? Or would restructuring the way the database is be an easier task? Thanks

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  • MySQL - Selecting the top occurring entries

    - by RC
    Hi, Should be a simple one. Database is mydb. One of the columns is mydata. What SELECT query do I need in order to select the top 3 occurring results from mydata, but sorted alphabetically? For example, if my data is this: mydata ====== kilo (x 1 occurrence) lima (x 9 occurrences) golf (x 5 occurrences) echo (x 9 occurrences) zulu (x 8 occurrences) How do I get it to return "echo, lima, zulu", which are the top three frequently occurring entries sorted alphabetically? Thanks! EDIT: Just to add, they need to be distinct entries. Thanks!

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  • Ordering by multiple columns in mysql with subquery

    - by Scarface
    Hey guys I have a query that selects data and organizes but not in the correct order. What I want to do is select all the comments for a user in that week and sort it by each topic, then sort the cluster by the latest timestamp of each comment in their respective cluster. My current query selects the right data, but in seemingly random order. Does anyone have any ideas? select * from ( SELECT topic.topic_title, topic.topic_id FROM comments JOIN topic ON topic.topic_id=comments.topic_id WHERE comments.user='$user' AND comments.timestamp>$week order by comments.timestamp desc) derived_table group by topic_id

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  • block write access to table from an application in mysql

    - by hoberion
    Hello, We have a CMS plugin that writes statistics to 1 table, this creates performance issues on the entire platform. We decided to use another statistics plugin which can connect to a different database server (the first plugin couldn't!) however we need parts of the first plugin. I want to lock the statistics table to prevent misusage (not allowed to drop it by the developer) So I was wondering if a lock table could do this or if I can implement some sort of read only table

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  • PHP MySQL Select multiple tables

    - by Jordan Pagaduan
    Is it posibble to select 3 tables at a time in 1 database? Table 1: employee -- employee_id -- first_name -- last_name -- middle_name -- birthdate -- address -- gender -- image -- salary Table 2: logs -- log_id -- full_name -- employee_id -- date -- time -- status Table 2: logout -- log_id -- full_name -- employee_id -- date -- time -- status I wanted to get the value of employee table where $id of selected. Then the $id also get the value of log.time, log.date, logout.time, and logout.date. I already try using UNION but nothing happens.

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  • Partitioning a table in mysql after creation

    - by erik
    I have a table with a bunch of data already in it. I know how to create a partitioned table or alter an already existing partitioned table, but can I add partitions to a table after it has been created, has data in it, without losing the data? The other option is to dump all the data, recreate the table with the partitions and then insert it all back it. Is that the only way? Thanks.

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  • Big problem with fluent nhibernate, c# and MySQL need to search in BLOB

    - by VinnyG
    I've done a big mistake, now I have to find a solution. It was my first project working with fluent nhibernate, I mapped an object this way : public PosteCandidateMap() { Id(x => x.Id); Map(x => x.Candidate); Map(x => x.Status); Map(x => x.Poste); Map(x => x.MatchPossibility); Map(x => x.ModificationDate); } So the whole Poste object is in the database but I would have need only the PosteId. Now I got to find all Candidates for one Poste so when I look in my repository I have : return GetAll().Where(x => x.Poste.Id == id).ToList(); But this is very slow since it loads all the items, we now have more than 1500 items in the table, at first to project was not supposed to be that big (not a big paycheck either). Now I'm trying to do this with criterion ou Linq but it's not working since my Poste is in a BLOB. Is there anyway I can change this easyly? Thanks a lot for the help!

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  • MySQL - mysqldump --routines to only export 1 stored procedure (by name) and not every routine

    - by Joe Stein
    So we have a lot of routines that come out from exporting. We often need to get these out in CLI, make changes and bring them back in. Yes some of these are managed by different folks and a better change control is required but for now this is the situation. If I do mysqldump --routines --no-create-info --no-data --no-create-db then great I have 200 functions I need to go through a file to find just the one or set I want. Is there anyway to mysqldump routines that I want like there is for tables???

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  • Mysql Avg function for recent 15 records by date (order date desc) in every symbol

    - by venkatesh
    i am trying to create a statement in sql (for a table which holds stock symbols and price on specified date) with avg of 5 day price and avg of 15 days price for each symbol. table description: symbol open high close date the average price is calculated from last 5 days and last 15 days. i tried this for getting 1 symbol: SELECT avg(close), avg(`trd_qty`) FROM (select * from cashmarket WHERE symbol = \'hdil\' order by `M_day` desc limit 0,15 ) s ...but I couldn't get the desired the list for showing avg values for all symbols.

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  • MySQL doesn't use index in join query

    - by Kocsonya Laci
    I have two tables: comments(id(primary key), author, ip(index)) and visitors(id(primary key), date_time, ip(index)) I want to join them like that: SELECT visitors.date_time FROM comments LEFT JOIN visitors ON ( comments.ip = visitors.ip ) WHERE comments.author = 'author' LIMIT 10 It works, but very slow.. In EXPLAIN it shows that it doesn't use the index on the visitors table: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE comments ref author author 78 const 9660 Using where 1 SIMPLE visitors ALL NULL NULL NULL NULL 8033 Any ideas? Thanks!

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  • mysql data being inserted twice via php

    - by Jascha
    I can't for the life of me figure out why this function is causing multiple entries into my database table... When I run the function I end up with two records stacked on top of each one second apart here is the function: function generate_signup_token(){ $connection = new DB_Connect(); // <--- my database connection class $ip = mysql_real_escape_string($_SERVER['REMOTE_ADDR']); $sign_up_token = uniqid(mt_rand(), true); $_SESSION['signup_token'] = $sign_up_token; $sign_up_token = mysql_real_escape_string($sign_up_token); $query = "INSERT INTO `token_manager` (`ip_address`, `signup_token`) VALUES ('$ip', '$sign_up_token')"; mysql_query($query); } generate_signup_token();

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  • mysql conditional query - complicated!

    - by emre
    i want to get distinct values for a field, let say: field1... ok this needs a query like: "select distint(field1) from table" however for some records, field1 is empty and there is another column that is an alternative to field1, which is field2. now; for the records where field1 is empty i need to use the value of field2. i think i need sort of a conditional select statement with if control something like: "select distinct( (if(field1!='') field1 else field2) ) from table" but i have no idea on how to write it. any help is appricated...

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  • mysql get table based on common column between two tables

    - by Zentdayn
    while trying to learn sql i came across "Learn SQL The Hard Way" and i started reading it. Everything was going fine then i thought ,as a way to practice, to make something like given example in the book (example consists in 3 tables pet,person,person_pet and the person_pet table 'links' pets to their owners). I made this: report table +----+-------------+ | id | content | +----+-------------+ | 1 | bank robbery| | 2 | invalid | | 3 | cat on tree | +----+-------------+ notes table +-----------+--------------------+ | report_id | content | +-----------+--------------------+ | 1 | they had guns | | 3 | cat was saved | +-----------+--------------------+ wanted result +-----------+--------------------+---------------+ | report_id | report_content | report_notes | +-----------+--------------------+---------------+ | 1 | bank robbery | they had guns | | 2 | invalid | null or '' | | 3 | cat on tree | cat was saved | +-----------+--------------------+---------------+ I tried a few combinations but no success. My first thought was SELECT report.id,report.content AS report_content,note.content AS note_content FROM report,note WHERE report.id = note.report_id but this only returns the ones that have a match (would not return the invalid report). after this i tried adding IF conditions but i just made it worse. My question is, is this something i will figure out after getting past basic sql or can this be done in simple way? Anyway i would appreciate any help, i pretty much lost with this. Thank you. EDIT: i have looked into related questions but havent yet found one that solves my problem. I probably need to look into other statements such as join or something to sort this out.

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  • mysql - combining columns and tables

    - by Phil Jackson
    Hi, I'm not much of a SQL man so I'm seeking help for this one. I have a site where I have a database for all accounts and whatnot, and another for storing actions that the user has done on the site. Each user has their own table but I want to combine the data of each user group ( all users that are "linked together" ) and order that data in the time the actions took place. Heres what I have; <?php $query = "SELECT `TALKING_TO` FROM `nnn_instant_messaging` WHERE `AUTHOR` = '" . DISPLAY_NAME . "' AND `TALKING_TO` != ''"; $query = mysql_query( $query, $CON ) or die( "_error_ " . mysql_error()); if( mysql_num_rows( $query ) != 0 ) { $table_str = ""; $select_ref_clause = "( "; $select_time_stamp_clause = "( "; while( $row = mysql_fetch_array( $query ) ) { $table_str .= "`actvbiz_networks`.`" . $row['TALKING_TO'] . "`, "; $select_ref_clause .= "`actvbiz_networks`.`" . $row['TALKING_TO'] . ".REF`, "; $select_time_stamp_clause .= "`actvbiz_networks`.`" . $row['TALKING_TO'] . ".TIME_STAMP`, "; } $table_str = $table_str . "`actvbiz_networks`.`" . DISPLAY_NAME . "`"; $select_ref_clause = substr($select_ref_clause, 0, -2) . ") AS `REF`, "; $select_time_stamp_clause = substr($select_time_stamp_clause, 0, -2) . " ) AS `TIME_STAMP`"; }else{ $table_str = "`actvbiz_networks`.`" . DISPLAY_NAME . "`"; $select_ref_clause = "`REF`, "; $select_time_stamp_clause = "`TIME_STAMP`"; } $where_clause = $select_ref_clause . $select_time_stamp_clause; $query = "SELECT " . $where_clause . " FROM " . $table_str . " ORDER BY TIME_STAMP"; die($query); $query = mysql_query( $query, $CON ) or die( "_error_ " . mysql_error()); if( mysql_num_rows( $query ) != 0 ) { }else{ ?> <p>Currently no actions have taken place in your network.</p> <?php } ?> The code above returns the sql statement: SELECT ( `actvbiz_networks`.`john_doe.REF`, `actvbiz_networks`.`Emmalene_Jackson.REF`) AS `REF`, ( `actvbiz_networks`.`john_doe.TIME_STAMP`, `actvbiz_networks`.`Emmalene_Jackson.TIME_STAMP` ) AS `TIME_STAMP` FROM `actvbiz_networks`.`john_doe`, `actvbiz_networks`.`Emmalene_Jackson`, `actvbiz_networks`.`act_web_designs` ORDER BY TIME_STAMP I really am learning on my feet with SQL. Its not the PHP I have a problem with ( I can quite happly code away with PHP ) I'ts just help with the SQL statement. Any help much appreciated, REgards, Phil

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  • How do I write this GROUP BY in mysql UNION query

    - by user1652368
    Trying to group the results of two queries together. When I run this query: SELECT pr_id, pr_sbtcode, pr_sdesc, od_quantity, od_amount FROM ( SELECT `bgProducts`.`pr_id`, `bgProducts`.`pr_sbtcode`, `bgProducts`.`pr_sdesc`, SUM(`od_quantity`) AS `od_quantity`, SUM(`od_amount`) AS `od_amount`, MIN(UNIX_TIMESTAMP(`or_date`)) AS `or_date` FROM `bgOrderMain` JOIN `bgOrderData` JOIN `bgProducts` WHERE `bgOrderMain`.`or_id` = `bgOrderData`.`or_id` AND `od_pr` = `pr_id` AND UNIX_TIMESTAMP(`or_date`) >= '1262322000' AND UNIX_TIMESTAMP(`or_date`) <= '1346990399' AND (`pr_id` = '415' OR `pr_id` = '1088') GROUP BY `bgProducts`.`pr_id` UNION SELECT `bgProducts`.`pr_id`, `bgProducts`.`pr_sbtcode`, `bgProducts`.`pr_sdesc`,SUM(`od_quantity`) AS `od_quantity`, SUM(`od_amount`) AS `od_amount`, MIN(UNIX_TIMESTAMP(`or_date`)) AS `or_date` FROM `npOrderMain` JOIN `npOrderData` JOIN `bgProducts` WHERE `npOrderMain`.`or_id` = `npOrderData`.`or_id` AND `od_pr` = `pr_id` AND UNIX_TIMESTAMP(`or_date`) >= '1262322000' AND UNIX_TIMESTAMP(`or_date`) <= '1346990399' AND (`pr_id` = '415' OR `pr_id` = '1088') GROUP BY `bgProducts`.`pr_id` ) TEMPTABLE3; it produces this result +-------+------------+--------------------------+-------------+-----------+ | pr_id | pr_sbtcode | pr_sdesc | od_quantity | od_amount +-------+------------+--------------------------+-------------+-----------+ | 415 | NP13 | Product 13 | 5 | 125 | 1088 | NPAW | Product AW | 4 | 100 | 415 | NP13 | Product 13 | 5 | 125 | 1088 | NPAW | Product AW | 2 | 50 +-------+------------+--------------------------+-------------+-----------+</pre> What I want to get a result that combines those into 2 lines: +-------+------------+--------------------------+-------------+-----------+ | pr_id | pr_sbtcode | pr_sdesc | od_quantity | od_amount +-------+------------+--------------------------+-------------+-----------+ | 415 | NP13 | Product 13 | 10 | 250 | 1088 | NPAW | Product AW | 6 | 150 +-------+------------+--------------------------+-------------+-----------+</pre> So I added GROUP BY pr_id to the end of the query: SELECT pr_id, pr_sbtcode, pr_sdesc, od_quantity, od_amount FROM ( SELECT `bgProducts`.`pr_id`, `bgProducts`.`pr_sbtcode`, `bgProducts`.`pr_sdesc`, SUM(`od_quantity`) AS `od_quantity`, SUM(`od_amount`) AS `od_amount`, MIN(UNIX_TIMESTAMP(`or_date`)) AS `or_date` FROM `bgOrderMain` JOIN `bgOrderData` JOIN `bgProducts` WHERE `bgOrderMain`.`or_id` = `bgOrderData`.`or_id` AND `od_pr` = `pr_id` AND UNIX_TIMESTAMP(`or_date`) >= '1262322000' AND UNIX_TIMESTAMP(`or_date`) <= '1346990399' AND (`pr_id` = '415' OR `pr_id` = '1088') GROUP BY `bgProducts`.`pr_id` UNION SELECT `bgProducts`.`pr_id`, `bgProducts`.`pr_sbtcode`, `bgProducts`.`pr_sdesc`,SUM(`od_quantity`) AS `od_quantity`, SUM(`od_amount`) AS `od_amount`, MIN(UNIX_TIMESTAMP(`or_date`)) AS `or_date` FROM `npOrderMain` JOIN `npOrderData` JOIN `bgProducts` WHERE `npOrderMain`.`or_id` = `npOrderData`.`or_id` AND `od_pr` = `pr_id` AND UNIX_TIMESTAMP(`or_date`) >= '1262322000' AND UNIX_TIMESTAMP(`or_date`) <= '1346990399' AND (`pr_id` = '415' OR `pr_id` = '1088') GROUP BY `bgProducts`.`pr_id` ) TEMPTABLE3 GROUP BY pr_id; But that just gives me this: +-------+------------+--------------------------+-------------+-----------+ | pr_id | pr_sbtcode | pr_sdesc | od_quantity | od_amount +-------+------------+--------------------------+-------------+-----------+ | 415 | NP13 | Product 13 | 5 | 125 | 1088 | NPAW | Product AW | 4 | 100 +-------+------------+--------------------------+-------------+-----------+ What am I missing here??

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  • MYSQL: How to limit inner join?

    - by Sergii Rechmp
    I need some help with my query. I have 2 tables: all: art|serie sootv: name|art|foo I need to get result like name|serie. My query is: SELECT t2.NAME, t1.serie FROM ( SELECT * FROM `all` WHERE `serie` LIKE '$serie' ) t1 INNER JOIN sootv t2 ON t1.art = t2.art; it works, but sootv table contains data like name|art|foo abc | 1 | 5 abc | 1 | 6 i get 2 same results. Its not what i need. Help me please - how i can get only one result: abc|1 Thanks.

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  • mysql insert and buffers, is this possible

    - by Grumpy
    how is this possible first i do insert into table2 select * from table1 where table1.id=1 ( 50k records should be moved 6 indexes has to be updated ) second delete from table1 where id=1 ( 50k records are removed ) How is it possible that only 45k of records are moved? Im scratching my head over this and cant find a right answer Is it possible that the insert is still active and delete already started

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  • In MYSQL is it better to have one big table or many smaller tables

    - by user307922
    Hi All, I am making a database of my client's customers to send email promotions to. The database will include all about 12 of my clients and each of them has an average of 2100 customers. I was wondering if it would be better to have a table in the db for each one of my clients that contains a list of their customers or if I should just make one big table... The customers will be queried daily. I know it is a broad question but any advice would be appreciated. Cheers, Chuck

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