MySQL : Open-Source, Relational Database Management System

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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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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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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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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 ...
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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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MySQL and window functions

It seems that MySQL does not support window functions. E.g. the simple: COUNT(*) OVER() AS cnt does not work. What I am not sure is if this applies to commercial version as well (I assume the ...
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PostgreSQL vs. MySQL - Advantages / Disadvantages with a spatial component

We are the in the process of building out a web application that has a spatial data component. In the beginning our spatial data comparisons will take a given point and return matched overlapping ...
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Any better way out of MySQL InnoDB log “in the future”?

I've got this InnoDB error in MySQL 5.0. Mysqld was stopped cleanly, but I managed to lose ib_logfile0 & ib_logfile1 afterward. Now after a clean startup, InnoDB has done its "crash recovery". ...
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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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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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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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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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Alternatives to MySQL Workbench

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 ...
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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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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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Why are simple SELECTs on InnoDB 100x slower than on MyISAM?

I have quite an annoying problem. I want to use INNODB as my main database engine and give up on MyISAM as I need the former for using galera-cluster for redundancy. I copied (description follows) ...
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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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What are the benefits of using MySQL Cluster?

I have never dipped my hands in MySQL Cluster and want to know how it can benefit me. When is it best to use it, and does it have performance benefits?
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Does making a field unique make it indexed?

If I make a unique constraint on a field, do I also need to make an index on that field in order to get a scalable insert time? Or is this done for me (even if the index it uses isn't publicly ...
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Generating Invoices and Tracking

Every 2 weeks, the system will generate the invoices for the companies. Company will receive an invoice on the 1st and 16th every month. (It will run via Cron Job every 2 week. It scan through the ...
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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... ...
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What is the usage of performance_schema in MySQL 5.5?

I have upgraded to MySQL version 5.5. There, I had observed performance_schema in the schema list. What is the usage of this new schema..? How can we monitor using this schema..? What are the ...
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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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MySQL LDAP authentication

Is LDAP authentication and authorization in MySQL possible? What are the requirements (MySQL version, third-party software etc.)? How it's organized? Thanks.
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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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MySQL Partitioning: Is there a performance tradeoff between number of partitions and size of each partition?

I have a large table (several 100 million rows) that I would like to efficiently partition. My question is whether there is a tradeoff between partition size and number of partitions. As far as I ...
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Too many columns in MySQL

I have a table with 1699 columns and when I'm trying to insert more columns I get the too many columns in the table error. In this table I have only 1000 rows. For me the most important thing is the ...
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How to create a database for unknown kinds of data?

I am in the process of designing a database for a new PHP/MySql-based application. My problem is that I do not and cannot represent what should be saved in the database because it is unlimited and ...
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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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MySQL : DROP TABLE Starting with a Prefix

EXAMPLE : I have more than 30 tables starting with a prefix "dp_" and about 12 starting with "ex_". QUESTION : How can I drop all tables starting "dp_" in one query ?
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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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How to select specific rows if a column exists or all rows if a column doesn't

I'm writing a script that gets a count of rows for a few tables, however for some tables I want to only get a count of rows where a flag is set (in this case active=1). Is there a way I can do this ...
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Data Compression Through Base36 Encoding

I'm trying to store a lot of large numbers that truncate when stored as INT values. Unfortunately they are too large for this type. I'm thinking about using Base36 encoding to accomplish this. Are ...
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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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Modify DEFINER on Many Views

I have am having problems backing up my databases after an update. I have been poking around on my system trying to figure out why. One query I ran returned this result. Got error: 1449: The user ...
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How to do a case sensitive search in WHERE clause?

I want case sensitive search in SQL query. But by default, MySQL does not consider the case of the strings. Any idea on how to do a case sensitive search in SQL query?
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How to configure global charset on MySQL

I tried to change the charset for our MySQL via my.cnf and it failed. I added the charset settings listed below: # The MySQL server [mysqld] port = 3306 socket = ...
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What is the purpose of the USING parameter in SQL?

Working with some code on a standard MySQL database, and I came across this statement: SELECT * FROM foo LEFT JOIN bar USING ('bar_id') WHERE foo_id = 1 What's throwing me is: what is USING for, ...
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Replicating a remote MySQL database to MS SQL Server 2008

I want to replicate the contents of a MySQL database to a MS SQL Server 2008 database. Is this possible? Can anyone outline the steps required in order to achieve this? Thanks.
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For a MySQL query, how do you determine physical and logical I/O?

I'm used to having a showplan in Microsoft SQL and have gotten lazy with using tools to tune MySQL queries. How can I determine physical/logical I/O for a query in MySQL? (EXPLAIN shows the index ...
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How to drop empty tables

Is it possible to drop all empty tables from my huge database (mysql)? I'm looking for a sql command to automatically remove all those empty tables. Currently, I have 305 tables in my dataset, and ...
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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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Is there a performance gain by handling data with stored procedures versus feeding it into functions after retrieval?

Title sums it up. I'm reasonably well off with PHP, and comfortable getting it to do what I need it to with values pulled from MySQL, however in the interest of expanding my knowledge I've been ...
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Alternative Database Tools for Web Admin

I currently use phpmyadmin for most of my database administration. It works well enough, but I'm interested in other tools that might work more quickly/efficiently/etc... What are the best and/or ...
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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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Deleting all duplicates

I am trying to delete all the duplicates but keeping single record only (shorter id). Following query deletes duplicates but take lot of iterations to delete all copies and keeping original ones. ...
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How to Best Implement nearest neighbour search in mysql?

So, in short, What should be the data type of latitude and longitude? What SQL command I should call to get the first 100 nearest restaurants for example? Detail: I have 100k biz record each with ...
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I am using the MEMORY storage engine but MySQL still writes to my disk…Why?

I am using the MEMORY Engine for all tables associated with a particular MYSQL query because speed of access is paramount to my project. For some reason, I have noticed that a large amount of disk ...
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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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Slow MySQL Database Import with mysqldump and USE .. SOURCE

I have about 12 tables in MySQL innoDB, one of them has 11 million records in it. I used this command to back things up: mysqldump -u [USERNAME] -p [DBNAME] | gzip > [/path_to_file/DBNAME].sql.gz ...