MySQL : Open-Source, Relational Database Management System

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ib_logfile opened with O_SYNC when innodb_flush_method=O_DSYNC

mysql will open and flush data/log files as below when innodb_flush_method=O_DSYNC Open log Flush log Open datafile Flush data O_SYNC NONE NONE fsync () ...
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8 views

DB Design Payments Table

I'm working on a Desktop application that uses a DB to store information i.e (customers, houses, proprietors, payments). So the application must accept payments from customers to company, company to ...
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1answer
174 views

MYSQL Timezone support

We are having a shared hosting plan and they are saying that do provide MYSQL Timezone support in a shared hosting plan. I can create timezone related tables in our database and populate them with ...
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1answer
107 views

Improve MySQL Query Performance - Too many records

I am using MySQL RDMS for a contact management system. Now a days my database grew in size and contains more than 1 million records. Checking duplicate phone numbers became a big issue during ...
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1answer
201 views

Designing database with Category and Tags for Posts - Seeking for guidance/advice

I'm not really a database novice but I'm not an expert either. Problem: I'm having this difficulty on designing my Post, Category and Tags relationship. I've read Normalization many times but could ...
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1answer
1k views

MySQL requires FORCE INDEX on huge table and simple SELECTs

We have an application which stores articles from different sources in a MySQL table and allows users to retrieve those articles ordered by date. Articles are always filtered by source, so for client ...
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1answer
46 views

Can I estimate the row count of a large mysql table using the disk space?

Sysadmin here (not a developer by trade), so go easy please ;) I have a mysql table, on a linux server that uses innodb_file_per_table. When I try to do select count(foo) from table; It doesn't ...
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1answer
90 views

MySQL thread states when changing an in-memory temporary table to disk-based

In High Performance MySQL (3rd edition) they state that: You can't tell whether a table was created in memory and then converted to on-disk or just created on-disk to begin with... What I was ...
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2answers
186 views

How to migrate data from SQL database to MySQL including flat files?

one of my friend has asked some asp developer to make online application where user can upload files also. jpg, doc, pdf and all these files are saved in SQL database as flat file. Now my friend asked ...
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10 views

Disable MySQL binary logging with log_bin variable

Default MySQL config file /etc/mysql/my.cnf installed by some debian package using APT often set log_bin variable, so binlog are enabled: log_bin = /var/log/mysql/mysql-bin.log When I want to ...
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1answer
26 views

MySQL: How turning off the logging affect the performance?

OS: RHEL5 DB: MySQL 5.1.73 community edition DB size: ~1GB I have setup a testing environment and turned off all logging - general logs, binary logs, slow query logs etc. I am using Oracle ...
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8 views

Amazon RDS CPU Usage keep increasing without any long running process in Show Processlist

We are using Amazon RDS(db.m2.2xlarge), CPU usage is suddenly increasing gradually even after we reboot the DB Server. This is happening just past 2 days and we didn't give any new build recently. I ...
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1answer
17 views

MySQL server performance plummets

Part of our software solution is responsible for processing files that get uploaded to us by our clients. We want to process them as quickly as we can. Our system is architected so that there's a ...
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2answers
27 views

InnoDB import performance

I'm struggling with bulk importing a quite big InnoDB-Table consisting of roughly 10 Million rows (or 7GB) (which for me is the biggest table I've worked with so far). I did some research how to ...
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1answer
111 views

How can i import 150GB database after deleting ibdata1,logfile in MYSQL?

I have 150GB database and my ibdata1 file size is 240GB so i want shrink the ibdata1 file so for that i have to export the DB and then drop the tables and then stop mysql, delete the ibdata1 file and ...
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21 views

How to optimize having bit_or?

Let's start with SQLFiddle http://www.sqlfiddle.com/#!2/64fc5/1 I have some urls and I am making some tasks (crons) related to them. Task can be successful or not. I want to try to do it only three ...
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1answer
19 views

Schema design - Reference slightly different data in different tables

I'm trying to design a schema for a MySQL database and got stuck on the following. My database stores documents which should have relations with blocks of content. create table document ( `id` ...
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3answers
5k views

Is there a way to recover a dropped mysql database?

I accidentally dropped a MySQL database on my server. Are there any ways to recover a dropped database?
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1answer
25 views

Restore InnoDB to different machine

It was pointed to me from serverfault that the following question would be a better fit here so this is basically my original question from there. I currently have backups that were taken with ...
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2k views

Difference between count(*) and count(1) in mysql?

In MySql we can count the total number of records by using count(1) or count(*). Is there any technical difference between them?
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106 views

Find the user with closest taste of mine

I trying to write in SQL the following requirement: Each user can rate as much films as they like. (1= I don't like, 5=I love it) And the system should provide to the current user a list of films ...
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2answers
67 views

JOIN on variable number of columns

I have the two tables courses AND something_about_courses: courses course_code course_session course_type something_about_courses course_code course_session some_description To ensure that I ...
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2answers
80 views

MYSQL Optimize tables on Innodb in production environment advice

According to mysqltunner.pl I have 177 Fragmented tables. I have over 5000 tables and 200 databases. If I run optimize table on each of them, do you think I should take down the application to ...
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1answer
43 views

How to export a MySQLtable with a longBLOB column to an Oracle database?

In MySQL I have a table: Select * from Dummy; Columns like below: id name salary binary_col 1 a 100 A.pdf 2 b 200 b.pdf 3 c 300 c.pdf 4 d 400 d.pdf 5 e 500 e.pdf ...
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1answer
35 views

Database design suggestions for a data scraping/warehouse application?

I'm looking into the database design for a data warehouse kind of project which involves a large number of inserts daily. The data archives will be further used to generate reports. I will have a ...
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1answer
10 views

How to minimize the writes needed to update a counter field multiple times

I need to minimize the number of queries that are executed just for updating a counter field. One of my example counter fields is raised by 1 everytime a page is visited, I was wondering what could ...
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1answer
33 views

How to write a complicated query in MySQL

I use MySQL on Linux. My table is about 8,000,000 rows. The table has indexes on advertiser_id, activity_date and activity_date, advertiser_id, activity_type. The table looks like: activity_date ...
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145 views

MySQL relay log rotates too soon and too often

I have a simple master/slave setup where the slave is just a backup. Sometimes I notice that the relay log on the slave rotates too often and too soon, when it is still very small: 4:00 PM ...
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1answer
52 views

Different column for different conditions when joining

I am using MySQL database and in that two tables, relation is one to many. One table is product table, sample data: +----+----------+ | id | name | +----+----------+ | 1 | product1 | | 2 | ...
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1answer
19 views

InnoDB internals - checkpoint, LSN, dirty pages

I'm looking into innodb internals regarding buffer pool and checkpoint, dirtypage. However there isn't enogh information to answer my question. When I run show global status, I can get ...
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1answer
120 views

Database design for mobile app

At first I would like to say hello to all of you, since it is my first post here on DB Administrators. I am writing an app which store drinks and their data. At the beginning it was storing all in ...
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1answer
65 views

Inconsistent MySQL query execution times

We run tests on two servers: one in production [Old Server] and the other one in tests [New Server]. Both tests used the same database. [New Server] Dedicated MySQL 5.6.17 server on Ubuntu 14.04 ...
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2answers
40 views

Msg 2627 Violation of PRIMARY KEY constraint

trying to make a database for teams in a tv show here. but when I try and insert data into tblShowteam the following error made its appearance. Msg 2627, Level 14, State 1, Line 2 Violation of ...
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15 views

MySQL Referential Integrity Issue

I'm having a lot of issues and don't really know where to look. I'm pretty sure it's a referential integrity issue and has something to do with the addition of the Professor table and the Foreign Key ...
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1answer
689 views

MySQL - run SELECT statement on another server without defining the table structure

In MySQL I can query information on another server using federated tables, as long as I've defined the same table structure locally. In MS SQL Server, however, I can run any SQL statement against a ...
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1answer
122 views

MySQL replication using a lot of IO

I'm having big troubles on a database pool I've setup recently. There is a master, and 4 slaves replicating one DB. All using MyISAM engine. Thing is, during the replication period (when the slave ...
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1answer
231 views

Inserting empty string on Windows MySQL doesn't use default value

Why inserting '' on a column with default integer value on MYSQL/WINDOWS produces ERROR 1366 (HY000): Incorrect integer value: '' for column 'id' at row 1 The query is: insert into test2 (id,test) ...
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19 views

Problems with foreign keys in a mysql database

I am trying to link both these tables with a foreign key. But I keep getting error message "ERROR 1452: Cannot add or update a child row: a foreign key constraint fails " the foreign key is pwalk_id ...
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1answer
61 views

Installing MySQL in Solaris

I am trying to install MySQL 5.5 on Solaris 10. I executed the code useradd -r -g mysql mysql where a group called mysql is already created using groupadd command. I get the following error : UX: ...
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Replication of a remote MySQL database to local MySQL database

I'm the developer of my employers corporate private website, a HTML5/PHP/CSS powered site for company reports etc. The site, hosted on a shared hosting package, connects to a remote read-only MySQL DB ...
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1answer
20 views

Using MySQL Workbench, what is a good way to do development on an alternate server and copy changes to the main server?

This is a noobie question. I'm taking over a database project from someone who recently left the company and I'm looking for advice on how to do some development on a test platform before making ...
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3answers
89 views

Restore large MySQL dump thorugh EasyPHP

I am trying to upload large files on easyphp but as there is limitation on this software and large databases cannot be uploaded. Is there some other software that allows to import large databases? ...
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2answers
44 views

Query to Access a specfic data in the row using python

Am using wordpress and phpmyadmin for handling my database Below is the code I use to view entries on my form using python. In the form I ask users to check/uncheck specific questions. It works as ...
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4answers
824 views

How can I replicate some tables without transferring the entire log?

I have a mysql database that contains some tables with private information, and some tables with public information. I would like to replicate only the tables containing public information from one ...
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0answers
21 views

MySQL Optimisation

I am running mySQL 5.6.16 on a server running Centos with 20Gb RAM ad 1TB disc space. when running SELECT scripts wiht order and group by statements and a number of joins, the results can be very slow ...
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1answer
25 views

Intermittent connection errors

I am experiencing occasional connection errors from my webserver to one of my databases. The code attempts to connect. If it fails, it sleeps for 1 second, then retries, then (if it still fails) ...
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1answer
63 views

Need help optimizing query to prevent full table scans

I have the following query, which while it works, is also doing a full scan on each left joined table (the log* tables). I thought by using a subquery in the FROM that this would eliminate the ...
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19 views

How to make changes to MySQL database settings

I'm a real DBA newbie and have learnt everything in the last day, so need basic guidance on how to implement the recommendations from MySQLTuner (which i eventually managed to do!) >> ...
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8k views

Why can't this mysql user log in with password?

In phpmyadmin I created a user called "edward" with password and all privileges: Yet when I try to log in via phpmyadmin, it says "Cannot log in to the MySQL Server". When I try to log in on the ...
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1answer
38 views

Options to include with mysqldump when taking backup of hybrid databases

I'm planning on taking backups of all MySQL databases on a remote production server. The combined database size is around 2 GB. Most of the tables are InnoDB ~1.8 GB and the rest are MyISAM. Now I've ...