MySQL : Open-Source, Relational Database Management System

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Why is MySQL is creating so many temporary tables on disk?

Can any configuration mistake lead to creating too many temp tables by mysql..mysql tuner shows Current max_heap_table_size = 200 M Current tmp_table_size = 200 M Of 17158 temp tables, 30% were ...
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3answers
6k views

How to convert mysql to postgresql? [closed]

I am desperately looking for a conversion tool to convert a big mysql database to postgresql. I need the tool/script to be: Free Works under Linux Simple to use and not buggy You actually tried and ...
9
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2answers
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Should I increase max_connections in AWS RDS t1-micro for MySQL?

I have an AWS RDS t1-micro running MySQL 5.5. It gives me too many connections error. I checked and it allows 34 maximum connections concurrently. What I have read is that i can increase this max ...
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2answers
7k views

move data folder and drive mysql centos

i need to move the data to a different folder and drive on my cent os db server. i added new hard drive (since we ran low on space), i have a 1tb of hard drive and i have a new 2tb i want to put the ...
9
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1answer
234 views

Power went out - Did query finish?

Is there a way to check and see if a query finished? I ran 3 very long running update queries (+/- 25 hours each) as I went out the door for vacation last week. Unfortunately, somewhere during the ...
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3answers
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MySQL High Performance for Lots of SELECTs/INSERTs/UPDATEs/DELETEs

I am creating a module where every user often gets a record into a table for 10 to 300 seconds. When the time expires a record gets deleted. The case is: there will be a lot of users and records will ...
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3answers
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How to get the most out of MySQL on a QuadCore machine with 16 GB of RAM?

I'm running a MySQL 5.5 server on my workstation for scientific data analysis and wonder how to configure MySQL in order to get the most out of it performance-wise. The types of query that I typically ...
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3answers
685 views

Is a 5+ column primary key bad for large (100 million+) table?

I was reading about some real life DB issues, and one project had a 100 million row plus table that had 5 columns as its primary. I'm thinking this is bad, but can anyone tell me exactly why? EDIT: ...
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1answer
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Is there such thing as Custom Data Types?

Does MySQL have any support for custom data types? For example, zip codes might be stored in a varchar(10) field, but they could be compacted in to an int, with options for blank, and a flag as to ...
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3answers
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MySQL status variable Handler_read_rnd_next is growing a lot

In MYSQL status, Handler_read_rnd_next value is very high. I am aware that, this value will be incremented when a query is executed which is not having proper indexes. But, even when we execute ...
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4answers
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Adding an index very slow…is there a mysql cmd to get an ETA or show progress?

I'm currently running an alter query on my table (20M entries) in order to add an index. it's running for more than 3 days already (stuck on 'copy to tmp table'). is there a way I can see the ...
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1answer
582 views

Calculate MATCH() AGAINST() scores from UNIFIED QUERY not FOR EACH TABLE

I am trying to have a score for entire section of SELECT statements SELECT *,MATCH(`result`) AGAINST('keyword') as `score` FROM `table1` WHERE MATCH(`result`) AGAINST('keyword') UNION SELECT ...
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9answers
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Which DBMS are fast enough for an online game (few thousand players)?

I'm currently making an MMORPG game, which could have a few thousand players online at the same time (probably not; just wishful thinking). First we wanted to use MySQL, but I have heard it isn't fast ...
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2answers
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Is it safe to delete mysql-bin files?

I have MM Replication in mysql, and I want to squeeze some free space in the box be deleting unnecessary files, I came across these mysql-bin files inside /var/db/mysql/ There are hundreds of those ...
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7answers
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slow load speed of data from mysqldump

I've got a moderate size MySQL database with about 30 tables, some of which are 10 million records, some 100 million. The mysqldump of all the tables (into separate files) is fairly fast, takes maybe ...
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3answers
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One Big Database vs. Several Smaller Ones

We have a situation were we can (A) deploy instances of an applications in one MySQL database using table prefixing or (B) use different MySQL databases for each instance of the application, for e.g., ...
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1answer
2k views

Is PostgreSQL replication production ready?

How does PostgreSQL native replication compare to MySQL? I know asynchronous replication has been supported for longer than sync, which is recent. Is synchronous reliable to be used in real projects? ...
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2answers
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For absolute performance, is SUM faster or COUNT?

This relates to counting the number of records that match a certain condition, e.g. invoice amount > $100. I tend to prefer COUNT(CASE WHEN invoice_amount > 100 THEN 1 END) However, this is ...
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5answers
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Why is DROP DATABASE taking so long? (MySQL)

New CentOS installation. I was running an import of a large DB (2GB sql file) and had a problem. The SSH client seemed to lose the connection and the import seemed to freeze. I used another window to ...
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2answers
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What to set innodb_buffer_pool and why..?

I have 170GB of InnoDB index and Data. I have to readjust the innodb_buffer_pool size for better performance.The Max table size of a InnoDB table(Index+data) is 28GB. So what should be the optimal ...
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2answers
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How do I show the binlog_format on a MySQL server?

How do I show the binlog_format on a MySQL server? And if I dont like it how do I set it to XX permanently? Where XX is STATEMENT, ROW or MIXED.
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4answers
859 views

Is splitting a 'users' table for authentication purposes a good idea?

Suppose I have a user table in my site in which there are around 2-3 Million users (records) in the table. For speeding up my login process, is it a good approach to split my user table, one for ...
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5answers
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Matching single column against multiple values without self-joining table in MySQL

We have a table that we use to store answers to questions. We need to be able to find users that have certain answers to particular questions. So, if our table consists of the following data: user_id ...
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2answers
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What is the safest way to switch the binlog format at runtime?

Because of the following warning in mysqld.log: [Warning] Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT. The statement is unsafe because it ...
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3answers
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mysql wont start after increasing innodb_buffer_pool_size and innodb_log_file_size

I am following this solution here http://stackoverflow.com/questions/3927690/howto-clean-a-mysql-innodb-storage-engine/4056261#comment14041132_4056261 and tried to increase my innodb_buffer_pool_size ...
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3answers
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How to stress test a SQL server?

I've been tasked to stress test our MSSQL Server and MySQL Server. I would like to know if there are any tools or scripts which I could use on our current systems and the new system to compare ...
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2answers
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What is the difference between optimize table and analyze table in mysql

What is the difference between optimize table and analyze table in mysql? I have read the online docs, but not sure what the difference is.
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5answers
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Fastest way to check if InnoDB table has changed

My application is very database intensive. Currently, I'm running MySQL 5.5.19 and using MyISAM, but I'm in the process of migrating to InnoDB. The only problem left is checksum performance. My ...
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6answers
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What could be causing strange query timeouts between PHP and MySQL?

I am the senior developer on a Software-as-a-Service application used by many different customers. Our software runs on a cluster of Apache / PHP application servers, powered by a MySQL backend. On ...
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4answers
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How can I optimize this MySQL query further?

I have a query that is taking a particularly long time to run (15+ seconds) and it is only getting worse with time as my dataset grows. I have optimized this in the past, and have added indices, ...
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5answers
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How to search a MySQL database with encrypted fields

Suppose I need to encrypt certain table-fields of a MySQL database. Additionally, I need to search some of those fields I did encrypt. How would one search those fields anyway? Decrypting each ...
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What tools are there for data masking? (MySQL, Linux) [closed]

I'm looking for (ideally free, open-source) data masking tools. Do any such exist? Note: this related question deals with tools for generating test data, but in this question I'm more interested in ...
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3answers
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Dynamic SQL in MySQL stored routines

According to the restrictions on stored routines and triggers, dynamic sql cannot be used (restriction lifted for stored procedures in version 5.0.13 and later). Why is this limitation in place? And ...
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2answers
318 views

Why would MySQL do serial synchronous I/O?

When looking at a particularly annoying query over MyISAM tables which takes a long time to execute on a number of occasions, I have noted that MySQL seems to expose a rather strange I/O pattern: when ...
8
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1answer
621 views

Deleting large amounts (4 million rows) of mysql data efficiently, on a very regular basis

We have a mysql table that at any given time has about 12 million rows. We need to delete old data to keep the size of the table somewhat manageable. Right now we are running this query daily, at ...
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2answers
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How do I shrink the innodb file ibdata1 without dumping all databases?

InnoDB stores all tables in one big file ibdata1. After dropping a big table, the file is keeping its size no matter how big the table was. How can I shrink that file without having to dump and ...
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3answers
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Monitor MySQL activity per database?

What is the best way to monitor activity on each database of my server ? I tried mtop/mytop which display activity in real time but aren't very practical to see all the queries executed on it. I ...
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3answers
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How do you re-sync the Master MySQL DB with Slave DB changes if the Master goes offline?

MySQL Server 1 is running as Master. MySQL Server 2 is running as Slave. With both DBs online, they are in "perfect sync". If Slave goes offline, there's no problem if Master still online; they will ...
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2answers
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How to use prepared statements within MySQL stored procedures?

I'm using mysql and I need to somehow use the column curid returned by the prepared statement in the later query. I use prepared statements because as I've read, it is the only way to pass a variable ...
8
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1answer
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Error creating foreign key from MySQL Workbench

I'm trying to synchronize schema changes from MySQL Workbench to my database. I'm getting the following error when it tries to create a foreign key: Executing SQL script in server ERROR: Error 1005: ...
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1answer
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MySQL reads / writes per table

I am optimising our DB. Essentially I am trying to find the most written and the most read tables in our db. After that I will follow by sym-linking those tables into separate drives. Is there a way ...
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1answer
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Does mysqldump export indices, by default?

I played around a little with mysqldump and I was wondering, if it does export indices (FULLTEXT, INDEX,...) by default. I read up on it and I found this option: --disable-keys, -K which suggests, ...
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1answer
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MySQL Workbench Database Sizes

I'm trying to find the total size on the hard disk that all of my MySQL Workbench databases are using. Does anyone know of an easy way to figure this out? If nothing else, the default location ...
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6answers
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Alternatives to MySQL Workbench [closed]

I've been running into some problems with MySQL Workbench that I'm not sure will be able to be fixed (namely, what appears to be an old bug that may have resurfaced), so I'd like to be able to find a ...
8
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1answer
1k views

Is there an execution difference between a JOIN condition and a WHERE condition?

Is there a performance difference between these two example queries? Query 1: select count(*) from table1 a join table2 b on b.key_col=a.key_col where b.tag = 'Y' Query 2; select ...
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2answers
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How to cast an integer to a boolean in a MySQL SELECT clause?

I'm new here so be kind to me. I have the following scenario: I have many tables which, for the sake of simplicity, are represented in a View in my MySQL database. My problem is that I need a value ...
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4answers
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What are the trade offs for incrementing ids vs. fulltext keys for foreign key designs?

In a lot of relational database designs there are fields that are referenced in other tables. For example consider a user table with a unique username and a second table storing address data. One ...
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1answer
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Cannot drop anonymous user from mysql.user

I am trying to DROP the anonymous users from my mysql.users database. However, I have been getting odd behavior. When I enter the command: DROP User ''@'WOPR'; I was getting a generic error ...
8
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1answer
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Is it possible to change ENUM() lists?

I wasn't sure if changing ENUM() list isn't possible so I made a test. In MySQL v5.1.58 I made a test InnoDB table that contains one field called 'bool' of type ENUM('yes', 'no'). Then I executed... ...
8
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1answer
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How does MySQL return a result set from a stored procedure?

I'm trying to get my head around stored procedures for use in a web application. It seems to me that whatever the last statement is in a MySQL stored procedure is seems to be what gets treated as that ...