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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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  • How do i know if a mysql table is using myISAM or InnoDB Engine

    - by kamal
    I want to confirm if the statement below is indeed true: There is no way to specify a storage engine for a certain database, only for single tables, You can, however, specify a storage engine to be used during one session with: SET storage_engine=InnoDB; so you don't have to specify it for each table. How do i confirm, if indeed all the tables are using InnoDB All the tables were using myISAM.

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  • MySQL - How do I insert an additional where clause into this full-text search query

    - by Steven
    I want to add a WHERE clause to a full text search query (to limit to past 24 hours), but wherever I insert it I get Low Level Error. Is it possible to add the clause and if so, how? $query = "SELECT * WHERE story_time > time()-86400 AND MATCH (story_title) AGAINST ('".validate_input($_GET['q'])."' IN BOOLEAN MODE) AS Relevance FROM ".$config['db']['pre']."stories WHERE MATCH (story_title) AGAINST ('+".validate_input($_GET['q'])."' IN BOOLEAN MODE) HAVING Relevance > 0.2 ORDER BY Relevance DESC, story_time DESC LIMIT ".validate_input(($_GET['page']-1)*10).",10";

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  • How to 'insert if not exists' in MySQL?

    - by warren
    I started by googling, and found this article which talks about mutex tables. I have a table with ~14 million records. If I want to add more data in the same format, is there a way to ensure the record I want to insert does not already exist without using a pair of queries (ie, one query to check and one to insert is the result set is empty)? Does a unique constraint on a field guarantee the insert will fail if it's already there? It seems that with merely a constraint, when I issue the insert via php, the script croaks.

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  • MySQL Join issue

    - by mouthpiec
    Hi, I have the following tables: --table sportactivity-- sport_activity_id, home_team_fk, away_team_fk, competition_id_fk, date, time (tuple example) - 1, 33, 41, 5, 2010-04-14, 05:40:00 --table teams-- team_id, team_name (tuple example) - 1, Algeria Now I have the following SQL statment that I use to extract Team A vs Team B SELECT sport_activity_id, T1.team_name AS TeamA, T2.team_name AS TeamB, DATE_FORMAT( DATE, '%d/%m/%Y' ) AS DATE, DATE_FORMAT( TIME, '%H:%i' ) AS TIME FROM sportactivity JOIN teams T1 ON home_team_fk = T1.team_id JOIN teams T2 ON ( away_team_fk = T2.team_id OR away_team_fk = '0' ) WHERE DATE( DATE ) >= CURDATE( ) ORDER BY DATE( DATE ) My problem is that when team B is empty, I am having irrelevant information .... it seems that it is returning all the combinations. I need a query that when team B is equal to 0, (this can occur in my scenario) I get only Team A - Team B (as 0) once.

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  • Union Distinct rows but order them by number of occurrences in mysql

    - by Baversjo
    Hi I have the following query: SELECT o.id,o.name FROM object o WHERE ( o.description LIKE '%Black%' OR o.name LIKE '%Black%' ) UNION ALL SELECT o2.id,o2.name FROM object o2 WHERE ( o2.description LIKE '%iPhone%' OR o2.name LIKE '%iPhone%' ) Which procude the following: id name 2 New Black iPhone 1 New White iPhone 2 New Black iPhone I would like to UNION DISTINCT, but I would also like the result ordered by the number of occurrences of each identical row (primary: id).

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  • MySQL ORDER BY rand(), name ASC

    - by Josh K
    I would like to take a database of say, 1000 users and select 20 random ones (ORDER BY rand(),LIMIT 20) then order the resulting set by the names. I came up with the following query which is not working like I hoped. SELECT * FROM users WHERE 1 ORDER BY rand(), name ASC LIMIT 20

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  • best way to prgram php and mysql query

    - by air
    most of times in our pages we need to print only 1 field value of table in loop. for example <?php for($i=1;$i<=mysql_num_rows($result);$i++) { echo $row['name']; $sql1="select industry from table_industry where profid='".$row['prof']."'"; $result1=mysql_query($sql1); $row1=mysql_fetch_array($result1); echo $row1['industry']; ?> } ?> above is one PHP code just for example where we think that $row['prof'] carry value of profession ID and we print profession of each person. for example we have 5000+ record in table and above loop will execute for 5000+ times what will be the best way to print value of industry field from table table_industry Same code which i write above ? any other php code suggestion for faster execution and less use of resources? Thanks

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  • How to refactor this MySQL code?

    - by Jader Dias
    SELECT * ( SELECT * FROM `table1` WHERE `id` NOT IN ( SELECT `id` FROM `table2` WHERE `col4` = 5 ) group by `col2` having sum(`col3`) > 0 UNION SELECT * FROM `table1` WHERE `id` NOT IN ( SELECT `id` FROM `table2` WHERE `col4` = 5 ) group by `col2` having sum(`col3`) = 0 ) t1; For readability and performance reasons, I think this code could be refactored. But how?

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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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  • MySQL - Join as zero if record Not IN

    - by Zurahn
    To explain by example, take two tables, A and B Table A id foo 1 x 2 y 3 z Table B id aid bar 1 3 50 2 1 100 An example join SELECT foo, bar FROM a, b WHERE a.id = b.aid; Garners a result of foo bar z 50 x 100 What I would like to do is get all values of foo and for any instances where there isn't a corresponding bar value, return 0 for that column. My best guess was something along the lines of SELECT foo, bar AS br FROM a, b WHERE a.id = b.aid OR a.id NOT IN (SELECT aid FROM b); But that returns duplicates and non-zero values for bar. Possible?

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  • many to many relationship mysql select

    - by zeina
    Let's consider 2 tables "schools" and "students". Now a student may belong to different schools in his life, and a school have many students. So this is a many to many example. A third table "links" specify the relation between student and school. Now to query this I do the following: Select sc.sid , -- stands for school id st.uid, -- stands for student id sc.sname, -- stands for school name st.uname, -- stands for student name -- select more data about the student joining other tables for that from students s left join links l on l.uid=st.uid -- l.uid stands for the student id on the links table left join schools sc on sc.sid=l.sid -- l.sid is the id of the school in the links table where st.uid=3 -- 3 is an example this query will return duplicate data for the user id if he has more than one school, so to fix this I added group by st.uid, yet I also need the list of school name related to the same user. Is there a way to do it with fixing the query I wrote instead of having 2 queries? So as example I want to have Luci of schools ( X, Y, Z, R, ...) etc

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  • MySQL: Question about SELECT WHERE AND/OR

    - by Andrew
    I'm trying to write a query that returns the same result from three different events, but I think I am doing it wrong. I can run my query against one event ID and it works. How can I select all three? Here's what I have so far: SELECT * FROM `Registrations` WHERE `Role` = "Attendee" AND `RegistrationStatus_ID` = "1" AND `DigSignature` IS NULL AND `Event_ID` = "147" OR `Event_ID` = "155" OR `Event_ID` = "160"

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  • mysql stored funtion usage

    - by shikhar
    I just wrote a stored function to calculate the working days between two dates. This works select CountWeekDays('2010-03-07','2010-04-07') This doesn't work select CountWeekDays(o.order_date,o.created_date) from orders o; Any idea how to make this one work ?? function definition delimiter $$; CREATE FUNCTION CountWeekDays (sdate VARCHAR(50), edate VARCHAR(50)) RETURNS INT BEGIN DECLARE wdays, tdiff, counter, thisday smallint; DECLARE newdate DATE; SET newdate := sdate; SET wdays = 0; if DATEDIFF(edate, sdate) = 0 THEN RETURN 1; END IF; if DATEDIFF(edate, sdate) < 0 THEN RETURN 0; END IF; label1: LOOP SET thisday = DAYOFWEEK(newdate); IF thisday BETWEEN 2 AND 6 THEN SET wdays := wdays + 1; END IF; SET newdate = DATE_ADD(newdate, INTERVAL 1 DAY); IF DATEDIFF(edate, newdate) < 0 THEN LEAVE label1; END IF; END LOOP label1; RETURN wdays; END

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  • Using a comma seperated data in MYSQL "IN" clause

    - by Sashi Kant
    I have a column in one of my table where I store multiple ids seperated by comma's. Is there a way in which I can use this column's value in the "IN" clause of a query. The column(city) has values like 6,7,8,16,21,2 I need to use as Select * from table where e_ID in (Select city from locations where e_Id=?) I am satisfied with Crozin's answer, but I am open to suggestions, views and options. Feel free to share your views.

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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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  • MySQL: INNER JOIN

    - by ABC
    I have a table which contains UserId & his Friends Id like: ---------------------------------------------- UserFriendsId | UserId | FriendId ---------------------------------------------- 1 1 2 ---------------------------------------------- 2 1 3 ---------------------------------------------- 3 2 1 ---------------------------------------------- 4 2 3 ---------------------------------------------- This table data shows that User-1 & User-2 are friend & they also have frndship with User-3. Now I want to find common friend(s) among UserId 1 & UserId 2 for eg: In sentance my query is: User 1 & User 2 have 1 common Friend FriendId 3. For this I used SQL query for INNER JOIN: SELECT t1.* FROM userfriends t1 INNER JOIN userfriends t2 ON t1.FriendId = t2.FriendId WHERE t1.UserId = 2 But not return required result..

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  • Get current session /process id from inside a mysql query

    - by Indra Ginanjar
    I'm trying to create a table for pseudo array variable. That looks like CREATE TABLE IF NOT EXISTS `MyArray`.`ArrayTable` ( `ID` INT UNSIGNED NOT NULL COMMENT 'Hash value of SessionID + ArrayName' , `SessionID` INT UNSIGNED NOT NULL , `ArrayName` CHAR(26) NOT NULL COMMENT '32 digit char - 6 digit longest process id (assumtion)' , `Index` INT UNSIGNED NOT NULL , `Value` TEXT NOT NULL , PRIMARY KEY (`ID`, `SessionID`) ) ENGINE = MyISAM; The table is not normalized yet, 'hope this will make it a little simpler to understand :) To avoid collission between client, there should be a differentiator between client session. For that reason i think need to know current session/process id (just like "SHOW PROCESSLIST") but really need to know IN WHICH process the query are?

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  • codeigniter active record and mysql

    - by sea_1987
    I am running a query with Active Record in a modal of my codeigniter application, the query looks like this, public function selectAllJobs() { $this->db->select('*') ->from('job_listing') ->join('job_listing_has_employer_details', 'job_listing_has_employer_details.employer_details_id = job_listing.id', 'left'); //->join('employer_details', 'employer_details.users_id = job_listing_has_employer_details.employer_details_id'); $query = $this->db->get(); return $query->result_array(); } This returns an array that looks like this, [0]=> array(13) { ["id"]=> string(1) "1" ["job_titles_id"]=> string(1) "1" ["location"]=> string(12) "Huddersfield" ["location_postcode"]=> string(7) "HD3 4AG" ["basic_salary"]=> string(19) "£20,000 - £25,000" ["bonus"]=> string(12) "php, html, j" ["benefits"]=> string(11) "Compnay Car" ["key_skills"]=> string(1) "1" ["retrain_position"]=> string(3) "YES" ["summary"]=> string(73) "Lorem Ipsum is simply dummy text of the printing and typesetting industry" ["description"]=> string(73) "Lorem Ipsum is simply dummy text of the printing and typesetting industry" ["job_listing_id"]=> NULL ["employer_details_id"]=> NULL } } The job_listing_id and employer_details_id return as NULL however if I run the SQL in phpmyadmin I get full set of results, the query i running in phpmyadmin is, SELECT * FROM ( `job_listing` ) LEFT JOIN `job_listing_has_employer_details` ON `job_listing_has_employer_details`.`employer_details_id` LIMIT 0 , 30 Is there a reason why I am getting differing results?

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  • Add results from MySQL?

    - by NardCake
    Not quite sure how descriptive that title was but this is what I want to do. I scripted a URL shortener today and it's working fine, I just want to add some stats on the bottom of it saying how many links there are and how many clicks there are. Now everytime a user clicks one of the links it +1 the column in the database then it redirects the user. I want to query that and add all of those numbers together from each row. I attempted a while loop which im not surprised didn't work: while($rows = mysql_fetch_assoc($check_count)){ $clicks = $rows['clicks']; $clicks = $clicks+$clicks; } If you don't understand please ask and if you do understand it means alot for any response!

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  • mysql select query optimization

    - by Saharsh Shah
    I have two table testa & testb. CREATE TABLE `testa` ( `id` INT(10) NOT NULL AUTO_INCREMENT, `name` VARCHAR(50) DEFAULT NULL, PRIMARY KEY (`id`) ); CREATE TABLE `testb` ( `id` INT(10) NOT NULL AUTO_INCREMENT, `name` VARCHAR(50) DEFAULT NULL, `aid1` INT(10) DEFAULT NULL, `aid2` INT(10) DEFAULT NULL, `aid3` INT(10) DEFAULT NULL, PRIMARY KEY (`id`) ); Currently I am running below query for retrieving all rows where id in testa table matches with any columns of aid1,aid2,aid3 in tableb. The query is retreiving acurate result but it is taking minimum 30 seconds to execute which is too much. I have also tried to optimise my query using UNION but failed to do so. SELECT a.id, a.name, b.name, b.id FROM testb b INNER JOIN testa a ON b.aid1 = a.id OR b.aid2 = a.id OR b.aid3 = a.id ; How do i optimize my query so it's total execution time is within 2-3 seconds? Thanks in advance...

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  • Find and replace braced tags within a MySQL table

    - by Cy
    I have about 40000 records in that table that contains plain text and within the plain text, contains that kind of tags which its only characteristic is that they are braced between [ ] [caption id="attachment_2948" align="alignnone" width="480" caption="the caption goes here"] How could I remove those? (replace by nothing) I could also run a PHP program if necessary to do the cleanup.

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