MySQL : Open-Source, Relational Database Management System

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Is index like key(timetime) usable when we query: SELECT * … ORDER BY timetime DESC

When we index a timestamp field like timetime. Can we use it for ORDER BY timetime DESC or is it just usable for ORDER BY timetime ASC OR ORDER BY timetime? Does mySQL use this index when doing vise ...
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What can we do in MySQL 5.0 Replication to address bandwidth concerns?

I am developing an application to run on the client PC (Win) which is configured with a MySQL server 5.1 instance that will act as read-only slave to the remote master. The remote master has dozens of ...
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2answers
303 views

MySQL Partitioning

I have a MyISAM table that holds a few million Messages. I am thinking about converting it to an partition InnoDB table. Just wondering about the best partition strategy. I would like to do this ...
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1answer
753 views

MySQL Handler_read_rnd_next == tablescans without indexes?

I am in the process of tuning our Percona 5.5 server, and have been using percona's tools to plot our database's performance. In the MySQL Handlers Plot, i have been noticing alot of ...
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2answers
102 views

MySQL using a index referencing a different column

I have a large table which uses a versioning system in the table. When a record is updated a new record is inserted with the old data and the original record is updated ( so to maintain the same ...
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495 views

Disable explicit commits in JDBC, detect them in SQL, or put the database in a readonly state

Background: I'm working on http://sqlfiddle.com (my site), and am trying to prevent one avenue of abuse possible there. I'm hoping that by asking about a problem I'm currently addressing, I don't ...
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Less restrictive query return less result due to simple removing one additional constraint

Look at this query SELECT DISTINCT TB.ID, TB.Latitude, TB.Longitude, 111151.29341326*SQRT(pow(-6.185-TB.Latitude,2)+pow(106.773-TB.Longitude,2)*0.98839228980165) AS Distance FROM ...
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Lock wait timeout exceeded on insert despite low lock_time in the slow query log

Our Java/Spring application reports occasional lock wait timeouts on single record INSERTs to a MySQL 5.5 InnoDB table. Here are a few slow query log records for some of the failed INSERTs. # ...
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MySQL insists on trying to use InnoDB even when told not to, please help

We're trying out MySQL 5.5, and have installed it on one of our slave servers as a test run. Our main server is 5.0, and we have zero optimization here for InnoDB, so I want everything to just be ...
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1answer
2k views

MySQL master binlog corruption

We recently made some changes to our infrastructure and now I can't keep MySQL replication running. The slave complains of a corrupt binlog and resetting it doesn't help. I keep seeing entries like ...
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String comparison with integer is not working sometimes in MySQL 5.5

I have upgraded MySQL to version 5.5. Before upgrading when we used string comparison with integer, it was working. Code is "value = 1", here 'value' is declared as varchar(45) and its value can be ...
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MySQL slave seems confused as to just how far out of date it is

I have a slave that claims, in SHOW SLAVE STATUS, to be zero seconds behind the master. However, it also says it's on Master_Log_File binlog.009636, which is 46.9 gig behind where the master is. I ...
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2k views

How can I tell if an index is being used to sort in MySQL?

I have a query with an ORDER BY clause which uses a column which is the last column on an index which is being used in the WHERE clause, essentially of the form: SELECT cols FROM tables WHERE ...
2
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1answer
499 views

Data type for protobuf objects in mysql

I would like to store some protobuf objects in a MySQL database. The objects are created in a Java application. The object is accompanied with a textual type identifier and a timestamp. ...
2
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1answer
2k views

Should I use WHERE NOT EXISTS or LEFT JOIN for getting the ids of relationship table?

I have users table: CREATE TABLE `users` ( `uid` mediumint(8) unsigned NOT NULL AUTO_INCREMENT, `email` varchar(70) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL, `flname` varchar(60), ...
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2answers
154 views

Copying a database for testing in a safe way

For testing purposes I have to create a copy of a production MySQL database that cannot be touched. These are the steps I would follow: Create a reduced size database backup: mysqldump prodDB ...
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1answer
3k views

How do you load a data file into a specific field?

How can I load data in a text file into a specific field. It's a 30 line log file from some copy operations; nothing fancy. I just want to store it as large text or a blob. The examples I am able to ...
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2answers
2k views

Best practices to secure mysql

I don't have that much knowledge about mysql and i would like to secure a MySQL server. We have a few VPS running around the world (6 currently) and they all need to store information in our mySQL ...
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1answer
2k views

MySQL - SELECT INTO OUTFILE, with a UNION

Is it possible to issue multiple select queries whose resultsets are combined via union, into the same outfile? What I am trying to do, but not working: (SELECT email FROM table WHERE createdate ...
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2answers
13k views

Can I execute a prepared statement inside a MySQL SELECT?

I'm running a search query in MySQL to return items from a products and pricelist table. When a user does a search query I need to get products from the products table LEFT JOINED with all ...
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1answer
2k views

MySql command line cyrillic Iinsert result is corrupted

Have putty connection. Putty config : window-->translation-->remote character set-->utf-8 Launch command line MySQL client. Perform insert with cyrillic like: CREATE TABLE `category` ( `catName` ...
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1answer
976 views

How to speed up mysql query?

I have query : SELECT `school`.`ARCO_name`, `student-`.`ClassSize_7`, `student-`.`ClassSize_8`, `degree_o`.`degree_code`, `accredit`.`full_faculty_3`, ...
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mySQL Relational Tables

Say I have 3 tables Products, Orders and Orders Product Products Table ID | StockNum | Description | Price 4 | 452SB | Black | 45.65 5 | 752SA | Green | 17.12 Orders Table ID ...
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A spatial query return no result when obviously there is result [duplicate]

Possible Duplicate: Less restrictive query return less result due to simple removing one additional constraint SELECT DISTINCT TB.ID, TB.Latitude, TB.Longitude, ...
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2answers
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Database Files-Related Issue

I am using MySQL database and using Ubuntu linux machine. I noticed that my database, db_test, is under the path /var/lib/mysql/db_test There are files with the suffix .frm, .MYD, .MYI like the ...
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How to manage a huge database?

We are building a service witch require a huge database. We are actually planning on getting more than 100 millions rows in our biggest table. So, what are the best options to store all this data in ...
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1answer
2k views

Any disadvantages of “SQL_BUFFER_RESULT” for MySQL SELECT?

I've been researching the usage of SQL_BUFFER_RESULT. Mostly it is referred to as an aid to reduce table lock issues. It seems to be a good option to use. However I cannot seem to find any ...
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1answer
466 views

Can I rollback/abort a transaction if no rows were inserted?

I have a transaction in which I want to do something like this: START TRANSACTION; INSERT INTO table1 (...) SELECT ... FROM table 2; ... if select count(*) from table1 returns 0 abort/rollback ... ...
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1answer
562 views

Is it possible to resume an interupted mysql import from a backup file?

I created a backup file of my database with phpMyAdmin and checked the following data dump option: include column names in every INSERT statement Example: INSERT INTO tbl_name ...
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2answers
152 views

How can I delete repeated rows?

I have a system that gathers RSS from many sites including UTF-8 based sites (non-english sites). I have tried to avoid repeated rows but I have repeats in my table. RSS_items (id(auto_increment) ...
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1answer
295 views

`SELECT FOR UPDATE` in master-master mysql setup

I am benchmarking a database schema with a dozen workers processes and was wondering what a SELECT FOR UPDATE does in a master-master configuration. For the moment it seems to work, but I am either ...
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MySql cluster data node replication

What I'd like to do is to replicate data nodes within a cluster not only for backup/failover purposes but also for scale-out reasons. Is this possible? If not: why? If yes: how do I do it? Actually, ...
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MYSQL Slow SELECT with multiple joins and ORDER BY

I have this query SELECT r0_.id AS id0, r0_.deleted_at AS deleted_at1, r0_.updated_at AS updated_at2, r0_.created_at AS created_at3, r0_.is_vehicle_offer AS is_vehicle_offer4, ...
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1answer
258 views

What storage engine should I use for this MySQL table?

I have a table where I store all the urls from my website, and I update them from time to time when a visitor enters. The primary key is the url itself varchar(255). I have set it to use InnoDB but ...
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2answers
417 views

MySQL upgrade on Ubuntu - any heads ups?

I am needing to upgrade MySQL on Ubuntu, it is a production server and naturally cautious. My many googles look to be essentially saying that I need to : Backup my current mysql database and ...
3
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1answer
121 views

Complex MySQL Query returning almost all the correct rows

I've created a SQLFiddle with my schema and some test data. The calculated columns aren't working for some reason in SQLFiddle, but they come out fine in my MYSQL Workbench. Assume they work ...
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4answers
836 views

best mysql field type for temperatures

I'm realising that this is the first time I've stored temperatures in a MySQL DB. What do think the best mysql field type for temperatures (c) is? Decimial (3,3) ?
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1answer
1k views

PDO count(*) does not work with LIMIT and OFFSET

here's my code it works normally, but this time i want to also count the records it gives. at the point of inserting COUNT(*) it will give NULL value to counted rows $query_list_records = ...
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1answer
385 views

Need help optimizing mysql on a busy server

I am managing a server for a very busy news website with lots of select queries (read-heavy), concurrent about 4000 users online at peak time. Around 1.4Mil pages views / day The server has 42G RAM, ...
2
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1answer
131 views

MySQL REPLACE appears to corrupt data

For reference, this issue was posted on StackOverflow.com before coming here. In MySQL I am running multiple REPLACE queries to update hardcoded URLs in a database. Queries look like this: UPDATE ...
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1answer
758 views

Delete by primary key takes too long

What would make a query that deletes a row using the primary key of the table .. take too long ? This is a table with about 1.4M rows that gets .. 70%/30% read/write . I don't know where to look. ...
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Why do we need myisam spatial extension anyway?

If just to determine whether a point is within a rectangle, What is wrong with this query? EXPLAIN SELECT DISTINCT TB.ID, TB.Latitude, TB.Longitude FROM TableBusiness AS TB WHERE ...
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Index Proposals

As a theoretical database question, if you are asked 'which indexes would you propose and why?' are the answers from primary, clustering and secondary index? How would we know if we should introduce ...
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One table with many rows or many tables with a few rows

I'm having a question rounding my mind. It's better to create one table and store a lot of rows there or create various tables and have a few rows on them? What's the performance and the I/O saved at ...
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1answer
284 views

MySQL Partition based on month-year

Is there a way that I can create a month-year partition on the below table? Without having to define all the permuations of month/year combos ? CREATE TABLE visitor_visits ( id int(10) UNSIGNED ...
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1answer
194 views

What is the SQL command to get 20 closest points from some center location

There are 1.6 million rows. Must not compute distance for all rows. Spatial index is available This is the table structure. The name of the table is businessauxiliary. So yes I used MyIsam, added ...
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MySQL function to return breadcrumb-like string from hierarchical structure

Show create table: CREATE TABLE `a` ( `id` int(11) NOT NULL, `name` varchar(255) DEFAULT NULL, `parent_id` int(11) DEFAULT NULL, PRIMARY KEY (`id`), KEY `parent_id` (`parent_id`), ...
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1answer
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MySQL transaction size - how big is too big?

I have an import process that runs every so often and I want it to be an 'all or nothing' kind of deal, aka: a transaction. There are many aspects, and the imports may yield anywhere between ...
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Centos 6.2 mysql configuration file help

I have a new centos 6.2 setup. Below is the configuration file. The machine is going to be fully innodb and it had 8Gb ram. What else must I include in the .cnf? [mysqld] datadir=/var/lib/mysql ...
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3answers
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This query is choking the server. How can I improve it?

Following query is hogging a lot of resources, as much as that the queries are getting locked down & CPU usage goes through the roof! The MySQL Processes list shows that as the number of requests ...