MySQL : Open-Source, Relational Database Management System

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How to get something written to MySQL error log without restart

I want to cause the MySQL 5.5 error log to be written to at will without a service stop or start. Note that I do not care what gets written to the error log, as long as something gets written. I ...
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1answer
425 views

Restoring Mysql Table From ibdata1, ib_logfile0, ib_logfile1 (without frm)

How to recover an innodb table that only left with ibdata, ib_logfile0 and ib_logfile1 without any frm file? Thanks
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1answer
51 views

what does !! as an operator in mysql?

I tried to use the exclamation mark as a not operator in a query SELECT !0, !!0, !!!0, !1, !!1, !!!1, !2, !!2, !!!2; | !0 | !!0 | !!!0 | !1 | !!1 | !!!1 | !2 | !!2 | !!!2 | ...
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2answers
4k views

How to sync two databases (alternative to mysql replication)?

Hello i have 2 mysql databases where most of the structure is constant except few tables (additions) in 2 dbs. I need to synchronize these 2 databases mainly common tables from one db to another. This ...
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25 views

Increasing limit by 1 results increases execution time from less than a second to infinite

Using a simple query like: select * from <table> limit 5; will return results in a fraction of a second, which is expected. I can increase the limit up to 49, and the results will still be ...
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1answer
118 views

Please suggest my.cnf configuration based upon mysqltuner findings

I have been facing a lot of slow browsing on my site nerdeky.com. My server administrator suggested me to use mysqltuner.pl to find and tune my databases. Can anyone select me what should be the good ...
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2answers
49 views

Prevent MySql from mangling queries by casting string to int

On one of my tables I have an auto incrementing ID field. It also has another field (richter_code) with a unique constraint but, over the seasons, this field can change - that's why I'm not using it ...
3
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1answer
360 views

Removing “duplicates” within a time range

I have a table that contains number plate data with a date and time stamp, collected by a plate-reading CCTV camera at a site entrance. Vehicles stopping at the site entrance will create multiple ...
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9answers
57k views
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250 views

MySql replication from 5.1 master to 5.6 slave keep crashing

I recently updated one of the replication slaves to mysql 5.6. After importing a recent dump from the master, I run mysql_upgrade with no errors. the database deamon started correctly with no ...
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1answer
25 views

Database query: join tags with exact matches or at least one

Given I have a query like: SELECT count(mm.id) AS c FROM merchant_mobile mm INNER JOIN mobile m ON mm.mobile_id = m.id LEFT JOIN merchant_mobile_customer mmc ON (mm.id = mmc.merchant_mobile_id) INNER ...
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135 views

Query multiple rooms with different conditionals (Adults, Children)

I have a simple query where I select available x Rooms with x Adults + x Children per hotel that matches a date range, but I'm having a hard time trying to figure out how to query a list of rooms per ...
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1answer
18 views

What should be the structure for a person-to-person store database

I am going to create a person-to-person store with Laravel, a website whose users can share and sell their product or their mobile, TV, Computer, Shoes, Shirts, Books ,Cars, Bags, Animal etc. I am ...
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1answer
20 views

How to report durations of 100+ queries in MySQL?

I have list of 142 SQL queries in an .sql file. At the beginning of this file I put SET profiling = 1;. At the end SHOW PROFILES;. I execute it with: mysql -u root live_copy < ...
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3answers
957 views

Mysql datatype for username of maximum 15 characters

I currently have a database with the "user" table having username as one of the columns. I allow a maximum of 15 characters for the username in my system... Is it fine to have the username column as ...
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22 views

MySQL Query Causing Massive Slowdown Over Time

I've been experiencing massive slowdown on my server after launching a new website. Using MONyog I can see that after an apache/mysql restart, the queries/second starts out nice and low for around 10 ...
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2answers
1k views

SQL Server to MySQL migration - how can I remove UCS-2 surrogate pairs in SQL Server?

I have been tasked with migrating a SQL Server 2005 database to MySQL 5.6 (these are both database servers runnig locally) and would really appreciate some help. -------Edit - Answered------- This ...
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1answer
503 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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4answers
7k views

Audit logins on MySQL database

Is there a way to audit logins to MySQL? I'd like to be able to create a username for each employee and thereby create an audit trail of logins. However, googling has turned up no good results. The ...
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1answer
548 views

Are there any disadvantages to partitioning on financial year?

Our current set up has one table per financial year (May 1- April 30). Each table has approx 1.5 million rows. We have about 8 years of data, and will obviously be adding each year. The majority of ...
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3answers
21 views

mysqld is generating a lot of disk IO writes. How can I figure out why?

I have a Ubuntu 14.04 server running half a dozen wordpress sites. Total traffic to the server is on the order of 30k page views a day. Over the past couple months, with page views and network ...
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0answers
758 views

MySQL connection timeout error retrieving big results

All of the sudden our MySQL 5.6 server (on Windows server) started to give us this error: "Lost connection to server during query". We never had this problem before and we haven't touch MySQL config ...
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2answers
758 views

How to run a cold backup with Linux/tar without shutting down MySQL slave?

I run the following before tar-ing up the data directory: STOP SLAVE; FLUSH TABLES WITH READ LOCK; FLUSH LOGS; However, tar will sometimes complain that the ibdata* and ib_logfiles* files are ...
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8 views

Performance/Maintenance Implications of a Write Heavy Table In An Otherwise Normal “CRUD” Database

We have a small-ish (<100,000 rows) MySQL database (on Amazon RDS). Its supporting a fairly simple read heavy CRUD web application. Currently we're building out a web analytics system. It will ...
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1answer
171 views

MySQL Available Cars With multiple owners

I have a complex SQL question. We are building a car rental system. We have a car model table, a owner table and a link_model_owner table. In addition our bookings are kept in another table. Scheme ...
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1answer
47 views

Transpose MySQL rows as column names - DYNAMIC

My goal is to be able to calculate the time difference between the ticket timestamp being created and closed and if reopened Add time from being reopened to closed again etc.. I have an existing mySQL ...
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1answer
28 views

Help with MySQL my.cnf config

So I'm running MySQL on a high availability cluster with the MySQL data directory on a GlusterFS. I want to: - Disable the query cache (--query-cache-size=0) - Switch on external locking ...
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2answers
58 views

MySQL to SQL Server - Unixtime being major problem

I'm trying to convert this query to SQL Server. It already has a lot of updates. Still, I don't know what to do from here ( i'm not the best when it comes to programming in MySQL ) SELECT ...
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1answer
36 views

converting mysql datebase

I have a question about converting mysql databases, I doing now new site, and want to use my old database, which is in latin_swedish_1 colacolation I want to convert this old database into ...
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1answer
2k views

MySQL: Lock wait timeout exceeded

I have a developer that has been trying to alter a large table (~60M rows). Via LiquidBase/JDBC they're running ALTER TABLE foo DROP FOREIGN KEY fk_foo_1; Today while it was running I checked in ...
3
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1answer
110 views

Stored Procedure to update an adjacency Model to Nested Sets Model

If you don't already know, these two models are the most common ways to store a tree in a relational DB. Adjacency Model: +-------------+----------------------+--------+ | category_id | name ...
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7 views

Database systems with users and sub users accessing the data

I am making a database for school student maintenance. Below is the basic description. There are schools. One school has many staff (i.e: Principles,Teachers, Section Head, Office Staff etc) These ...
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209 views

DB disk space requirements comparision between MySQL versions

I have 2 labs where MySQL is installed. DataBases are created and deleted dynamically by certain internal processes. InnoDB is the Engine used. In one lab, MySQL version 5.0.77 is installed. The DB ...
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1answer
94 views

Relaying changes to a slave from another master with Tungsten on MySQL

I am trying to setup a multi-master type of replication with each master having an additional slave using Tungsten. As an example, lets say I have 4 hosts (A,B,C,D) and hosts A and C are the masters, ...
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1answer
12 views

Mariadb refusing to read values on the my.cnf file

today i was optimizing my mariadb since my website was running too slow My machine is a Centos 7 , 4 gbs ram 3 cpu i runned a script called mysql_tuner.pl and the results were: -- MYSQL ...
2
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1answer
366 views

Alter mysql database engine doesn't work from cluster to other

I got into this issue when I tried to alter my database table engine to InnoDB from ndbcluster, It did not work. But When I changed engine from InnoDB to ndbcluster it worked. It did not throw any ...
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2answers
138 views

Dealing with data stored as arrays in a MySQL DB

So I know storing arrays in a DB field is wrong and would never do it myself, however a 3rd party plugin my company is using stores data in an array and I was wondering if you could help me try to ...
0
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1answer
2k views

Select from a list of values from JSON encoded data

I have saved the details of the product in JSON format. I am wondering how to select from a list of values from a "JSON_ENCODED DATA" For Example I want to select TV with screen_type as LED or LCD. ...
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2answers
924 views

How to fix slow LIMIT queries with big offsets without heavily rewriting them?

Imagine a very basic example of your average discussion board. For example: CREATE TABLE threads ( id INT UNSIGNED NOT NULL AUTO_INCREMENT, title VARCHAR(100), PRIMARY KEY (id) ) CREATE ...
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1answer
160 views

Get child record from specific root

I have two tables articles and topics and I am using MySQL 5.6 Articles id topic(fk on Topics.id) featured 1 1 1 2 2 0 3 3 ...
2
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1answer
473 views

How to normalize my db schema for a quiz application?

I am putting together a quiz application. (I'm calling each quiz a "challenge") I have a "challenge" table and a "challenge_question" table which is pretty straightforward. challenge table: id ...
7
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2answers
432 views

ROLLBACK doesn't work after INSERT INTO newly created destination table

I am working on PHP-script which imports CSV file (customers.csv) into MySQL table (customers). Before inserting contents of CSV-file into the mysql table I am first backing up the original customers ...
2
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1answer
192 views

Avoiding Multiple Queries when Searching for Records Associated with a Set of Records

So, I am sure I have done something really stupid while designing this, and I'm open to schema changes if they'll really help me out. On to the problem: I have a custom shopping cart system (backed ...
0
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1answer
26 views

How to reference categories table in products table?

I am using modified preorder traversal algorithm to store product categories in database (like image shown above). But i don't understand how to reference it in my products table. Here is my ...
0
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1answer
24 views

How bigger page size effect at performance?

I know in case of Cluster index bigger page size improve peformance for range and multipoint query. Does bigger page size can effect to degrade performance when we have non cluster index .Because ...
3
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3answers
373 views

Finding differences between a master and slave when pt-table-sync fails

I have a table that's showing some differences on a master and slave according to pt-table-checksum (PTC). I've found some verifying differences beyond that. Certain tables in the mix have composite ...
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Custom cycling order in MySQL

Having following Foo table: id | name | group ===|=========|====== 1 | "John" | 1 2 | "Paul" | 1 3 | "Marry" | 1 4 | "Josh" | 1 5 | "Mike" | 2 6 | "Kevin" | 2 7 | "Ramon" | 2 8 | "Kim" ...
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1answer
238 views

SQL table architecture

I'm looking for a SQL architecture solution for the following problem. The idea is that I have a validation form that contains the client's data. Each client can log in to his account and edit his ...
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13 views

MySQL View: Transform rows in columns and update

i would like to show data from this mysql-table: ID | Channel_ID | Value | Time | 01 | 15 | 10,5 | 364 | 02 | 3 | 4,2 | 365 | 03 | 3 | 5,3 | 394 | in an ...
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11 views

How I do a complete backup restore of MySQL Schema with views and functions?

I am trying to backup a single schema on a Windows server and restore it to an Ubuntu 12.04 Linux server running MySQL 5.5.4. The schema includes views and functions. When I used the MySQL Workbench ...