mysql query - Page 214 - Developer IT

help optimize sql query

- by msony

I have tracking table tbl_track with id, session_id, created_date fields I need count unique session_id for one day here what i got: select count(0) from ( select distinct session_id from tbl_track where created_date between getdate()-1 and getdate() group by session_id )tbl im feeling that it could be better solution for it

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Storing connections between people in a MySql database

- by daniel

I would like to create a database where I store the links between people. I then need to bring back the records detailing which people are connected to which others. I need to output: person1 is connected to person2 is connected with person3 etc. How can I get started with this task?

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Mysql Database Question about Large Columns

- by murat

Hi, I have a table that has 100.000 rows, and soon it will be doubled. The size of the database is currently 5 gb and most of them goes to one particular column, which is a text column for PDF files. We expect to have 20-30 GB or maybe 50 gb database after couple of month and this system will be used frequently. I have couple of questions regarding with this setup 1-) We are using innodb on every table, including users table etc. Is it better to use myisam on this table, where we store text version of the PDF files? (from memory usage /performance perspective) 2-) We use Sphinx for searching, however the data must be retrieved for highlighting. Highlighting is done via sphinx API but still we need to retrieve 10 rows in order to send it to Sphinx again. This 10 rows may allocate 50 mb memory, which is quite large. So I am planning to split these PDF files into chunks of 5 pages in the database, so these 100.000 rows will be around 3-4 million rows and couple of month later, instead of having 300.000-350.000 rows, we'll have 10 million rows to store text version of these PDF files. However, we will retrieve less pages, so again instead of retrieving 400 pages to send Sphinx for highlighting, we can retrieve 5 pages and it will have a big impact on the performance. Currently, when we search a term and retrieve PDF files that have more than 100 pages, the execution time is 0.3-0.35 seconds, however if we retrieve PDF files that have less than 5 pages, the execution time reduces to 0.06 seconds, and it also uses less memory. Do you think, this is a good trade-off? We will have million of rows instead of having 100k-200k rows but it will save memory and improve the performance. Is it a good approach to solve this problem and do you have any ideas how to overcome this problem? The text version of the data is used only for indexing and highlighting. So, we are very flexible. Thanks,

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Use of HAVING in MySQL

- by KBrian

I have a table from which I need to select all persons that have a first name that is not unique and that that set should be selected only if among the persons with a similar first name, all have a different last name. Example: FirstN LastN Bill Clinton Bill Cosby Bill Maher Elvis Presley Elvis Presley Largo Winch I want to obtain FirstN LastN Bill Clinton or FirstN LastN Bill Clinton Bill Cosby Bill Maher I tried this but it does not return what I want. SELECT * FROM Ids GROUP BY FirstN, LastN HAVING (COUNT(FirstN)>1 AND COUNT(LastN)=1)) [Edited my post after Aleandre P. Lavasseur remark]

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mysql - joining three tables with HAVING

- by Qiao

I have table: id name type where "type" is 1 or 2 I need to join this table with two other. Rows with "type = 1" should be joined with first table, and =2 with second. Something like SELECT * FROM tbl INNER JOIN tbl_1 ON tbl.name = tbl_1.name HAVING tbl.type = 1 INNER JOIN tbl_2 ON tbl.name = tbl_2.name HAVING tbl.type = 2 But it does not working. How it can be implemented?

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What is an index in MySQL?

- by Eric

http://i.imgur.com/JdsUK.jpg I created a table like the picture above. What are the "Indexes"? primary key? unique? It works well without setting indexes.. What do they do? why do I need them? Also, I set all String fields to TEXT because I didn't know how many characters I need. Is this a good idea? I don't see any difference. Thanks!

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mysql dynamic cursor

- by machaa

Here is the procedure I wrote- Cursors c1 & c2. c2 is inside c1, I tried declaring c2 below c1 (outside the c1 cursor) but then I is NOT taking the updated value :( Any suggestions to make it working would be helpful, Thanks create table t1(i int); create table t2(i int, j int); insert into t1(i) values(1), (2), (3), (4), (5); insert into t2(i, j) values(1, 6), (2, 7), (3, 8), (4, 9), (5, 10); delimiter $ CREATE PROCEDURE p1() BEGIN DECLARE I INT; DECLARE J INT; DECLARE done INT DEFAULT 0; DECLARE c1 CURSOR FOR SELECT i FROM t1; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1; OPEN c1; REPEAT FETCH c1 INTO I; IF NOT done THEN select I; DECLARE c2 CURSOR FOR SELECT j FROM t2 WHERE i = I; OPEN c2; REPEAT FETCH c2 into J; IF NOT done THEN SELECT J; END IF; UNTIL done END REPEAT; CLOSE c2; set done = 0; END IF; UNTIL done END REPEAT; CLOSE c1; END$ delimiter ;

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php, mySQL & AJAX: Unable to use sessions across the scripts in the same domain

- by Devner

Hi all, I have the following pages: page1.php, page2.php and page3.php. Code in each of them is as below CODE: page1.php <script type="text/javascript"> $(function(){ $('#imgID').upload({ submit_to_url: "page2.php", file_name: 'myfile1', description : "Image", limit : 1, file_types : "*.jpg", }) }); </script> <body> <form action="page3.php" method="post" enctype="multipart/form-data" name="frm1" id="frm1"> //Some other text fields <input type="submit" name="submit" id="submit" value="Submit" /> </form> </body> page2.php <?php session_start(); $a = $_SESSION['a']; $b = $_SESSION['b']; $c = $_SESSION['c']; $res = mysql_query("SELECT col FROM table WHERE col1 = $a AND col2 = $b AND col3 = $c LIMIT 1"); $num_rows = mysql_num_rows($res); echo $num_rows; //echos 0 when in fact it should have been 1 because the data in the Session exists. //Ok let's proceed further //... Do some stuff... //Store some more values and create new session variables (and assume that page1.php is going to be able to use it) $_SESSION['d'] = 'd'; $_SESSION['e'] = 'e'; $_SESSION['f'] = 'f'; if (move_uploaded_file($_FILES['file']['tmp_name'], $file)) { echo "success"; } else { echo "error ".$_FILES['file']['error']; } ?> page3.php <?php session_start(); if( isset($_POST['submit']) ) { //These sessions are non-existent although the AJAX request //to page2.php may have created them when called via AJAX from within page1.php echo $_SESSION['d'].$_SESSION['e'].$_SESSION['f']; ?> } ?> As the code says it I am posting some info via AJAX call from page1.php to page2.php. page2.php is supposed to be able to use the session values from page1.php i.e. $_SESSION['a'], $_SESSION['b'] and $_SESSION['c'] but it does not. Why? How can I fix this? page2.php is creating some more sessions after some processing is done and a response is sent back to page1.php. The submit button of the form on page1.php is hit and the page gets POST'ed to page3.php. But when the SESSION info that gets created in page2.php is echoed, it's blank signifying that SESSIONS from page2.php are not used. How can I fix this? I looked over a lot of information and have spent about 50 hours trying to do different things with my scripts before arriving at the above conclusions. My app. is custom made using function (not OOPS) and does not use any PHP frameworks & I am not even about to use any as my knowledge of OOP concepts is limited any many frameworks are object oriented. I came across race conditions, but the solutions provided don't help too much. One more solution of using DB to hold sessions and seek and retrieve from DB is the last thing on my mind and I really want to avoid creating table, coding and maintaining code for a task as simple as just keeping sessions across pages in the same domain. So my request is: Is there a way that I can solve the above problem(s) via simple coding in present conditions? Any help is appreciated. Thank you.

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data in mysql show after barcode split and matches character

- by klox

i need some code for the next step..this my first step: <script> $("#mod").change(function() { var barcode; barCode=$("#mod").val(); var data=barCode.split(" "); $("#mod").val(data[0]); $("#seri").val(data[1]); var str=data[0]; var matches=str.matches(/EE|[EJU]).*(D)/i); }); </script> after matches..i want the result can connect to data base then show data from table inside <div id="value">...how to do that?

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mysql check if numbers are in a comma separated list

- by Tillebeck

Hi I have a table like this: UID(int) NUMBERS(blob) ---------------------- 1 1,13,15,20 2 3,10,15,20 3 3,15 And I would like to test if 3 and 15 are in the blob called NUMBERS. And can see the LIKE %% cannot be used Only row with ID 2 and three scoulb be selected...

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MySQL - getting SUM of MAX results from 2 tables

- by SODA

Hi, Here's my problem: I have 2 identical tables (past month data, current month data) - data_2010_03, data_2010_04: Content_type (VARCHAR), content_id (INT), month_count (INT), pubDate (DATETIME) Data in month_count is updated hourly, so for each combination of content_type and content_id we insert new row, where value of month_count is incrementally updated. Now I try something like this: SELECT MAX(t1.month_count) AS max_1, MAX(t2.month_count) AS max_2, SUM(max_1 + max_2) AS result, t1.content_type, t1.content_id FROM data_2010_03 AS t1 JOIN data_2010_04 AS t2 ON t1.content_type = t2.content_type AND t1.content_id = t2.content_id WHERE t2.pubDate < '2010-04-08' AND t1.content_type = 'video' GROUP BY t1.content_id ORDER BY result desc, max_1 desc, max_2 desc LIMIT 0,10 I get an error "Unknown column 'max_1' in 'field list'. Please help.

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PHP mySQL - select unique value that not being used from dirrefent table

- by apis17

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auto_increment in MySQL - can I omit it?

- by kees-kist

I've noticed that PHPmyAdmin creates the following SQL for table creation: CREATE TABLE something ( ... ) auto_increment=1; When I write a database creation script I don't use the auto_increment bit. From reading related questions here I understand that it determines the starting value for auto_increment values. But it is good practice to reset it to 1, or should I just leave it out of the SQL so that the default is used?

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PHP Serialize Function - Adding serialized data to mysql and then fetch and display

- by Abhilash Shukla

I want to know whether the PHP serialize function is 100% secure, also if we store serialized data into a database and want to do something after fetching it, will it be a nice way. For example:- I have a website with different user privileges, now i want to store the permissions settings for a particular privilege to my database (This data i want to store is to be done through php serialize function), now when a user logs in i want to fetch this data and set the privilege for the customer. Now i am ok to do this thing, what i want to know is, whether it is the best way to do or something more efficient can be done. Also, i was going through php manual and found this code, can anybody explain me a bit what's happening in this code:- [Specially why base64_encode is used?] <?php mySerialize( $obj ) { return base64_encode(gzcompress(serialize($obj))); } myUnserialize( $txt ) { return unserialize(gzuncompress(base64_decode($txt))); } ?> Also if somebody can provide me their own code to show me to do this thing in the most efficient manner. Thanks.

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Caching Mysql database for better performance

- by kobey

Hi, I'm using Amazon cloud and I've performance issue since the HDD is not located on my machine. My database is small (~500MB) and I can afford to keep it all in my RAM. I do not want to keep queries in my RAM, i need all the tables there. How can i do it? Thanks, Koby P.S. I'm using ubuntu server...

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mysql 2 primary key onone table

- by Bharanikumar

CREATE TABLE Orders -> ( -> ID SMALLINT UNSIGNED NOT NULL, -> ModelID SMALLINT UNSIGNED NOT NULL, -> Descrip VARCHAR(40), -> PRIMARY KEY (ID, ModelID) -> ); Basically May i know ... Shall we create the two primary key on one table... Is it correct... Bcoz as per sql law,,, We can create N number of unque key in one table, and only one primary key only is the LAW know... Then how can my system allowing to create multiple primary key ? Please advise .... what is the general rule

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What does this MySQL statement do?

- by user198729

INSERT IGNORE INTO `PREFIX_tab_lang` (`id_tab`, `id_lang`, `name`) (SELECT `id_tab`, id_lang, (SELECT tl.`name` FROM `PREFIX_tab_lang` tl WHERE tl.`id_lang` = (SELECT c.`value` FROM `PREFIX_configuration` c WHERE c.`name` = 'PS_LANG_DEFAULT' LIMIT 1) AND tl.`id_tab`=`PREFIX_tab`.`id_tab`) FROM `PREFIX_lang` CROSS JOIN `PREFIX_tab`); It's from an opensource project,and no documentation available. Especially,what does cross-join mean? I've only used join/left join .

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Tricky MySQL Query for messaging system in Rails - Please Help

- by ole_berlin

Hi, I'm writing a facebook style messaging system for a Rails App and I'm having trouble selecting the Messages for the inbox (with will_paginate). The messages are organized in threads, in the inbox the most recent message of a thread will appear with a link to it's thread. The thread is organized via a parent_id 1-n relationship with itself. So far I'm using something like this: class Message < ActiveRecord::Base belongs_to :sender, :class_name => 'User', :foreign_key => "sender_id" belongs_to :recipient, :class_name => 'User', :foreign_key => "recipient_id" has_many :children, :class_name => "Message", :foreign_key => "parent_id" belongs_to :thread, :class_name => "Message", :foreign_key => "parent_id" end class MessagesController < ApplicationController def inbox @messages = current_user.received_messages.paginate :page => params[:page], :per_page => 10, :order => "created_at DESC" end end That gives me all the messages, but for one thread the thread itself and the most recent message will appear (and not only the most recent message). I can also not use the GROUP BY clause, because for the thread itself (the parent so to say) the parent_id = nil of course. Anyone got an idea on how to solve this in an elegant way? I already thought about adding the parent_id to the parent itself and then group by parent_id, but I'm not sure if that works. Thanks

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MySQL Select statement Where table1.id != table2.id

- by Michael

I have a table of data which has posts, then I have a separate table of data which has deleted posts. What happens when a post is deleted is that it's ID get's added to the deleted table rather than removing the post entry. What is a clean efficient way of selecting all the posts from the posts table without selecting the ones that have their ID in the deleted table

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sql query question / count

- by scheibenkleister

Hi, I have houses that belongs to streets. A user can buy several houses. How do I find out, if the user owns an entire street? street table with columns (id/name) house table with columns (id/street_id [foreign key] owner table with columns (id/house_id/user_id) [join table with foreign keys] So far, I'm using count which returns the result: select count(*), street_id from owner left join house on owner.house_id = house.id group by street_id where user_id = 1 count(*) | street_id 3 | 1 2 | 2 A more general count: select count(*) from house group by street_id returns: count(*) | street_id 3 | 1 3 | 2 How can I find out, that user 1 owns the entire street 1 but not street 2? Thanks.

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Import CSV to mysql

- by 404error

I have created a database and table. I have also created all the fields i will be needing. I have created 46 fields including 1 that is my ID for the row. The CSV doesn't contain the id field, nor does it contain the headers for the columns. I am new to all of this but have been trying to figure this out. I'm not on here being lazy asking for the answer, but looking for direction. I'm trying to figure out how to import the CSV but have it start importing data starting at the 2nd field, since I'm hoping the auto_increment will fill in the ID field, which is the first field i created. I tried these instructions with now luck. Can anyone offer some insight? your cvs file's column name must match your table column name browse your required .csv file select CSV using LOAD DATA options Check box 'ON' for Replace table data with file in Fields terminated by box type , in Fields enclosed by box " in Fields escaped by box \ in Lines terminated by box auto in Column names box type column name seperated by , like column1,column2,column3 10 check box ON for Use LOCAL keyword.

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Problems getting foreign keys working in MySQL

- by thehuby

I've been trying to get a delete to cascade and it just doesn't seem to work. I'm sure I am missing something obvious, can anyone help me find it? I would expect a delete on the 'articles' table to trigger a delete on the corresponding rows in the 'article_section_lt' table. CREATE TABLE articles ( id INTEGER UNSIGNED PRIMARY KEY AUTO_INCREMENT, url_stub VARCHAR(255) NOT NULL UNIQUE, h1 VARCHAR(60) NOT NULL UNIQUE, title VARCHAR(60) NOT NULL, description VARCHAR(150) NOT NULL, summary VARCHAR(150) NOT NULL DEFAULT "", html_content TEXT, date DATE NOT NULL, updated TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP )ENGINE=INNODB; CREATE TABLE article_sections ( /* blog, news etc */ id INTEGER UNSIGNED PRIMARY KEY AUTO_INCREMENT, url_stub VARCHAR(255) NOT NULL UNIQUE, h1 VARCHAR(60) NOT NULL, title VARCHAR(60) NOT NULL, description VARCHAR(150) NOT NULL, summary VARCHAR(150) NOT NULL DEFAULT "", html_content TEXT NOT NULL DEFAULT "" )ENGINE=INNODB; CREATE TABLE article_section_lt ( fk_article_id INTEGER UNSIGNED NOT NULL REFERENCES articles(id) ON DELETE CASCADE, fk_article_section_id INTEGER UNSIGNED NOT NULL )ENGINE=INNODB;

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How to match multiple field in mySQL

- by Mint

Im trying to match forum_id with several different forum_id's, something like forum_id = 5,7,12,43,63,78 I currently have this code: SELECT topic_title, topic_id, forum_id FROM $MYSQL_TOPIC WHERE topic_title LIKE '%%%s%%' AND forum_id = 5 LIMIT 50 (using mysql_real_escape_string and sprintf) I tried: forum_id = 5 OR 7 forum_id = 5|7 forum_id = 5 AND 7 forum_id = 5 & 7 But none of them will match them all and therefore search though them all.

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MySQL - Select all as one string

- by poru

How could I select all as one string seperated with a ,? Example table: Table Stringtest Examplestring2 Anotherstring Otherstring And the selected result should be Stringtest,Examplestring2,Anotherstring,Otherstring.

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Data truncation when retrieving data from MySQL database with prepared statements

- by KSiimson

I have a script that retrieves multiple products using prepared statements. Like putting loops into loops, I have prepared statements in prepared statements - so there is a prepared statement for retrieving all products, a prepared statement to retrieve all images for that product, a prepared statement to get all attributes for that products, and so on. This does not work with one MySQLi instance, so I use multiple MySQLi objects that are opened and closed when needed. It usually works fine, but sometimes, especially when displaying multiple products, some data is truncated. For example - MicoLoans becomes MicoLoa. There was an actual spelling mistake here - now when I changed MicoLoans to MicroLoans, the same page displayed MicroLoa... So the same number of characters was truncated from the end. It is sort of consistent where it appears - for example there can be descriptions for 8 products, and description of 1 product is heavily truncated. When I add 9th product, the short description is still truncated for that same product as before. Any ideas?

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