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  • Update all table rows but top N in Mysql

    - by arthurprs
    I was trying to run the following query UPDATE blog_post SET `thumbnail_present`=0, `thumbnail_size`=0, `thumbnail_data`='' WHERE `blog_post` NOT IN ( SELECT `blog_post` FROM blog_post ORDER BY `blog_post` DESC LIMIT 10) But Mysql doesn't allow 'LIMIT' in an 'IN' subquery. I think I can make a select to count the table rows and then make an ordered update limited by 'COUNT - 10', but I was wondering if there is a better way. Thanks in advance.

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  • mysql innodb:innodb_flush_method

    - by Daniel
    in the following link http://dev.mysql.com/doc/refman/5.1/en/innodb-parameters.html#sysvar_innodb_flush_method it says:Different values of this variable can have a marked effect on InnoDB performance. For example, on some systems where InnoDB data and log files are located on a SAN, it has been found that setting innodb_flush_method to O_DIRECT can degrade performance of simple SELECT statements by a factor of three. Why O_DIRECT could slow down the select statement?

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  • Efficient way to build a MySQL update query in Python

    - by ensnare
    I have a class variable called attributes which lists the instance variables I want to update in a database: attributes = ['id', 'first_name', 'last_name', 'name', 'name_url', 'email', 'password', 'password_salt', 'picture_id'] Each of the class attributes are updated upon instantiation. I would like to loop through each of the attributes and build a MySQL update query in the form of: UPDATE members SET id = self._id, first_name = self._first name ... Thanks.

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  • Which MySql line is faster:

    - by Camran
    I have a classified_id variable which matches one document in a MySql table. I am currently fetching the information about that one record like this: SELECT * FROM table WHERE table.classified_id = $classified_id I wonder if there is a faster approach, for example like this: SELECT 1 FROM table WHERE table.classified_id = $classified_id Wont the last one only select 1 record, which is exactly what I need, so that it doesn't have to scan the entire table but instead stops searching for records after 1 is found? Or am I dreaming this? Thanks

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  • accessing SQL syntax reference in mysql workbench

    - by dcompiled
    Finding it a little bit tedious migrating to the new Mysql Workbench (5.2.22) even though it has many more features than the older GUI tools. Right now I'm confused why I can't find an SQL reference when I open the Doc Library. Is there a way to access this info within the workbench, I'd prefer not to have to open a browser to access reference info on the web.

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  • MySQL Datefields: duplicate or calculate?

    - by Konerak
    We are using a table with a structure imposed upon us more than 10 years ago. We are allowed to add columns, but urged not to change existing columns. Certain columns are meant to represent dates, but are put in different format. Amongst others: * CHAR(6): YYMMDD * CHAR(6): DDMMYY * CHAR(8): YYYYMMDD * CHAR(8): DDMMYYYY * DATE * DATETIME Since we now would like to do some more complex queries, using advanced date functions, my manager proposed to d*uplicate those problem columns* to a proper FORMATTED_OLDCOLUMNNAME column using a DATE or DATETIME format. Is this the way to go? Couldn't we just use the STR_TO_DATE function each time we accessed the columns? To avoid every query having to copy-paste the function, I could still work with a view or a stored procedure, but duplicating data to avoid recalculation sounds wrong. Solutions I see (I guess I prefer 2.2.1) 1. Physically duplicate columns 1.1 In the same table 1.1.1 Added by each script that does a modification (INSERT/UPDATE/REPLACE/...) 1.1.2 Maintained by a trigger on each modification 1.2 In a separate table 1.2.1 Added by each script that does a modification (INSERT/UPDATE/REPLACE/...) 1.2.2 Maintained by a trigger on each modification 2. On-demand transformation 2.1 Each query has to perform the transformation 2.1.1 Using copy-paste in the source code 2.1.2 Using a library 2.1.3 Using a STORED PROCEDURE 2.2 A view performs the transformation 2.2.1 A separate table replacing the entire table 2.2.2 A separate table just adding the date-fields for the primary keys Am I right to say it's better to recalculate than to store? And would a view be a good solution?

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  • Inexplicably slow query in MySQL

    - by Brandon M.
    Given this result-set: mysql> EXPLAIN SELECT c.cust_name, SUM(l.line_subtotal) FROM customer c -> JOIN slip s ON s.cust_id = c.cust_id -> JOIN line l ON l.slip_id = s.slip_id -> JOIN vendor v ON v.vend_id = l.vend_id WHERE v.vend_name = 'blahblah' -> GROUP BY c.cust_name -> HAVING SUM(l.line_subtotal) > 49999 -> ORDER BY c.cust_name; +----+-------------+-------+--------+---------------------------------+---------------+---------+----------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+---------------------------------+---------------+---------+----------------------+------+----------------------------------------------+ | 1 | SIMPLE | v | ref | PRIMARY,idx_vend_name | idx_vend_name | 12 | const | 1 | Using where; Using temporary; Using filesort | | 1 | SIMPLE | l | ref | idx_vend_id | idx_vend_id | 4 | csv_import.v.vend_id | 446 | | | 1 | SIMPLE | s | eq_ref | PRIMARY,idx_cust_id,idx_slip_id | PRIMARY | 4 | csv_import.l.slip_id | 1 | | | 1 | SIMPLE | c | eq_ref | PRIMARY,cIndex | PRIMARY | 4 | csv_import.s.cust_id | 1 | | +----+-------------+-------+--------+---------------------------------+---------------+---------+----------------------+------+----------------------------------------------+ 4 rows in set (0.04 sec) I'm a bit baffled as to why the query referenced by this EXPLAIN statement is still taking about a minute to execute. Isn't it true that this query only has to search through 449 rows? Anyone have any idea as to what could be slowing it down so much?

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  • mysql category tree search

    - by ffffff
    I have the following schema on MySQL 5.1 CREATE TABLE `mytest` ( `category` varchar(32) , `item_name` varchar(255) KEY `key1` (`category`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1; category column is filled with like that [:parent_parent_cat_id][:parent_cat_id][:leaf_cat_id] "10000200003000" if you can search all of the under categories :parent_parent_category_id SELECT * FROM mytest WHERE category LIKE "10000%"; it's using index key1; but How to use index when I wanna search :parent_cat_id? SELECT * FROM mytest WHERE category LIKE "%20000%"; Do you have a better solutions?

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  • mysql meeting multiple conditions

    - by Djeux
    I'm having a table, where one ID, can have multiple statuses | client_id | status_id | | 1 | 2 | | 1 | 3 | | 1 | 5 | | 2 | 2 | | 2 | 3 | | 2 | 6 | The problem is, to select only those client_id's if they have all the statuses i.e. 2,3,5 (status_id = 2 AND status_id = 3 AND status_id = 5) but mysql doesn't allow that directly.

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  • MySQL friends table

    - by asmo
    I have a MySQL DB in which I store data about each user. I would like to add a list of friends for each user. Should I create a table of friends for each user in the DB or is there a better way?

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  • SQL query to remove text within parentheses?

    - by Josh Fraser
    What is the best SQL query to remove any text within parenthesis in a mySQL database? I'd like something that works regardless of the position of the parenthesis in the text (beginning, middle, end, whatever). I don't care about keeping the text inside the parenthesis, just removing it. Thanks!

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  • finding missing values, mysql??

    - by praveenmon
    i am using mysql database i have a table called sales its primary key is sales_id ------------------------------------- sales_id | invoice_id | ------------------------------------- 1 | 147 2 | 148 3 | 150 for sales-id 3 the invoice is supposed to be 149. i want to know which numbers are missing from invoice_id (i start invoice_id is 147 and end invoice_id is 4497). The invoice_id had no relation with sales_id is it possible to know which numbers are missing from invoice_id, using some queries??

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  • mysql get last auto increment value

    - by Mick
    Hi I have a field in mySql table called jobnumber which auto increments with each new entry. What I want to do is when a user views my form, get the value of the next 'jobnumber' . But I want to do this before any entry is made to the table. IE so when a user looks at a form it will display something like 'this is job number 6954' I have tried $rr = mysql_insert_id() but this only work after I have made an entry Can anyone help please thanks

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  • mysql command for update

    - by Mac Taylor
    hey guys i need to add a special text to all rows in my mysql table , how to add some text to the end of all rows' content in a table just for one field i used this code : UPDATE `blogs` SET `title`= `title`+ 'mytext'; but didnt work for me

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  • MySQL get variable from SELECT

    - by rlb.usa
    MySQL keeps saying my syntax is incorrect. I want to do this: DELIMITER $$ DROP PROCEDURE IF EXISTS `myprocedure` $$ CREATE DEFINER=`db`@`%` PROCEDURE `myprocedure`( var_name varchar(10) ) BEGIN /* syntax errors below */ DECLARE countTemp integer; SET countTemp=(SELECT COUNT(Name) FROM mytable WHERE Name= var_name); /* more stuff */ END $$ DELIMITER ; What's the correct syntax?

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