All versions of MySQL (not Microsoft SQL Server). Please also add a version-specific tag like mysql-5.7 if that is relevant to the question.

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5
votes
3answers
2k views

MySQL Query Optimization : Indexing and Pagination

I'm adding pagination to my 'latest news' php script and running in to an issue. SELECT sid, title, time, bodytext, author, url FROM news WHERE approved=1 ORDER BY time desc LIMIT $start, $limit I ...
2
votes
4answers
784 views

Best way to automate running several MySQL commands

We have several core db tables on our system and allow our employees access to these tables via views that just show them the data they need to see. We created these views in a new db specific to ...
5
votes
4answers
5k views

Storing arrays of integers in database (for efficient select)

I am creating a database that will store 100.000 (and probably more in the future) users. While this obviously happens in a table with 1 row per user, every user can (and will) store hundreds of ...
14
votes
1answer
470 views

Does anyone have a good recommendation for a book which teaches sharding?

Does anyone have a good recommendation for a book which teaches db sharding (from scratch at best) I have read like 40 different websites talking about sharding. I'm not saying online sites/blogs ...
6
votes
3answers
4k views

Too Many Connections

I'm using MATLAB to feed the database but after a time I'm getting a too many connections error. I always using opendb and closedb in pair. Is it to fast the feeding? Do I have to wait after I ...
2
votes
2answers
130 views

Database Agnostic Conditional

I'm writing a Drupal module and I want it to be agnostic between PostgreSQL and MySQL. I have a field that gets its value from a conditional, and I originally wrote it as an IF(). Then I found out ...
2
votes
1answer
517 views

Concurrent INSERTs in XtraDB (InnoDB)

I'm currently unable to insert rows concurrently in an XtraDB table on Percona Server 5.1.54. I had the same problem with a similar version of MySQL. My table definition is as follows. CREATE TABLE ...
0
votes
1answer
3k views

How to get query execution time and query result at the same time? [closed]

Is there any SQL query syntax that returns query execution time and query result at the same time?
8
votes
3answers
2k views

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 ...
3
votes
1answer
334 views

MySQL Replication not working properly on Ubuntu Lucid Lynx Server

I have two Linux boxes. On the master following is the configuration file (my.cnf) log-bin = master-bin log-bin-index = master-bin.index binlog-do-db = test_db server-id = 1 master ...
7
votes
3answers
2k views

Can you “su -” in MySQL?

If I have root on a mysql database and I want to drop privileges to that of a normal user, without using their password, can I do it? if so how? think # su - username on unix. Basically, I'm just ...
7
votes
2answers
1k views

MySQL connection doesn't work anymore

I had two MySQL servers running (127.0.0.1:3306 and 127.0.0.1:3307). Now I get this strange error: mysql_connect(): Lost connection to MySQL server at 'reading initial communication packet' I can ...
7
votes
1answer
9k views

How do you increase MySQL performance using current server resources?

I have a MySQL database and some of my queries became slow. Query time is not stable. Most of the queries are fast, but some of them (may be that reads and returns less data) take long time. I know ...
3
votes
1answer
615 views

MySQL CREATE statement are really slow (Mac OS X / Macport install) [closed]

I recently noticed that recreating the database for the web application I am working on is taking a lot of time. I had just reinstalled Mysql from Macport... I am getting really lousy performances, ...
9
votes
3answers
4k views

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 ...
4
votes
2answers
428 views

TOP X of SQL Server in MySQL Analog

I am looking for SQL Server TOP (X) Analog in MySQL In SQL Server: SELECT TOP 5 Z ... FROM ORDER BY Z DESC How can this be done in MySQL? ADDED: I have found for other RDBMS: Returning TOP N ...
8
votes
3answers
3k views

Users complain that system runs slow when mysqldump is in progress.

The MYSQL database (ibdata1) is of size 73 GB and is configured to run as a dedicated database server on Windows 2008 O/S for INNODB tables. We are running the backup using mysqldump mysqldump ...
5
votes
1answer
337 views

MySQL and Solid State Disks on EMC

Since all writes and sequential reads are cached by the EMC storage system, the best use for solid state disk is to store data that has a random READ pattern. On Oracle, that is the temp tablespace ...
39
votes
2answers
12k views

NULL or NOT NULL by default?

In MySQL, is it better to always allow nulls unless you know a field is required, or always use Not Null unless you know a field will contain nulls? Or doesn't it matter? I know in some DBMSs they ...
7
votes
4answers
3k views

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 ...
3
votes
3answers
1k views

Database Performance Tuning

I have a MySQL backend, MS Aaccess front-end system that is nice and responsive over a local network but becomes sluggish over a broadband connection. I haven't done any performance tuning as of yet. ...
5
votes
5answers
2k views

What is the best use of memory in MySQL?

I have a MySql server with 2Gb of memory. What's the best configuration to use then with best results? How can I "distribute" this memory fine to MySql server?
5
votes
1answer
510 views

MySQL Replication: Insert generating VERY huge temporary tables

our replication slave is generating ~300GB temporary files while running relatively simple inserts. Our setup: Master: 5.0.45-0.sles10.x86_64, Slave: 5.0.85-win32, also tried with 5.1.57-win64, ...
6
votes
3answers
8k views

Avoiding temporary tables while sorting by a column in a different table

So I have this MySQL InnoDB query here: SELECT s.vid, s.body, s.timestamp, COUNT(v.id) AS votecnt FROM stories s LEFT JOIN votes v ON s.vid = v.vid WHERE s.lv = 1 AND s.status = 1 GROUP BY s.vid ...
3
votes
3answers
3k views

MySQL and PostgreSQL Licence issue

Our Company wants to use MySQL for one software product. This product is not open-source. Is it legal to use it freely ? If not, how about PostgreSQL ? Is this okay for our purpose ?
2
votes
3answers
130 views

Can I automate the “on” statement from MySQL queries?

Background In the process of QA/QC, I am writing lots of queries with multiple joins. I am using MySQL. I would like to know how (if) I can simplify join statements, e.g. by setting default fields ...
2
votes
2answers
4k views

Storing images in MySQL db — type? [duplicate]

Possible Duplicate: Is it better to store images in a blob or just the url? I need to recover images from an XML file stored on a remote server and save it to my database. Not sure how I ...
3
votes
2answers
3k views

Why is mysqldump file so large?

We have a 2GB MySQL DB. We started a mysql dump of this DB this morning and the resulting dump file is 27GB! Can anyone shed some light on what's going on here? Questions Why is this file so ...
2
votes
3answers
2k views

What are the best practices for triggers to maintain a revision number on records?

I have an audit trail implemented on an application database that captures old value, new value, modification time, and user inserting it into another table. I'm now wanting to add a revision number ...
3
votes
1answer
3k views

MySQL - LOAD DATA INFILE - Handling unescaped NULL in INFILE or creating INFILE with escaped NULL

I am selecting data from a database on server A, dumping the output into a file locally, and then doing a LOAD DATA INFILE on my local database. The bash command looks something like this: mysql -e ...
5
votes
2answers
2k views

Creating partitions on a production database

I have a production MySQL 5.1 database that is running well but I want to improve query performances. I have never used Partitions and just going through the manuals. I have two tables that involve a ...
5
votes
2answers
5k views

Determine Reason for Deadlock in MySQL

We've been seeing some deadlocks occur but have not been able to reproduce. Is there any way to determine, after the fact, what queries were running, etc to figure out why deadlock occurred?
3
votes
1answer
1k views

MySQL InnoDB data file directly on a disk slice (fixed-size)?

It seems that ibdata1 is like a disk slice. In Solaris (UNIX) UFS filesystems (the common one before ZFS), one would separate their disk c0t0d0 into slices, say a 10GB drive would be cut into three ...
2
votes
1answer
1k views

Installing MySQL server 4.1 on Ubuntu 11.04

how do I need to install mySQL server 4.1 on Ubuntu 11.04 server for a legacy app to run (it breaks on mySQL 5). sudo apt-get mysql-server-4.1 doesn't work - "package is missing, obsoleted or ...
3
votes
2answers
331 views

How can I model this relationship?

My database design skills are a bit rusty so I was hoping to get some help from y'all =) I have a 'user' table that contains all the typical fields (id,name,email,etc.). Users can have many ...
4
votes
3answers
823 views

Improving slow queries. Slow query log attached

Below is the Slow Query Log when my .NET application was running. Please let me know how to improve the performance of the queries: TCP Port: 3306, Named Pipe: (null) Time Id Command ...
1
vote
1answer
324 views

Shift db data to another column

I have the following table id | ev_id | ev_loc_id | a | b | prev_a | prev_b If I the (ev_id AND ev_loc_id) not exist in the table then I just insert them, otherwise I'm putting ...
1
vote
3answers
1k views

Please review the My.INI settings of my PC. File Attached

Below is the my.ini file of one of my PC running MySQL 5.5 with 1 GB RAM. It is not using concurrent connections and we are using a stand-alone PC for a single application and single user. # MySQL ...
3
votes
1answer
941 views

Duplicate UNIQUE KEY error after ROLLBACK in MySQL

I have a table like this mysql> describe seudonimos; +--------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra ...
0
votes
1answer
4k views

Change path for binary logs and scheduling

I want to change the default name of binary log and path. I saw the documentation where it discusses about base_name. However, I just need to confirm how to use it correctly. I want binary logs to be ...
6
votes
3answers
12k views

Optimizing InnoDB default settings

I looked into my.ini and saw various default settings. My database is running on a single stand-alone PC. I want to optimize the performance of InnoDB and MySQL in general for performance. There is no ...
6
votes
2answers
14k views

Do INSERTs get auto-committed?

Our application fires an INSERT query to the MySQL Database to add records. I want to know whether or not the records get auto-committed. If I run the ROLLBACK command, when does the database perform ...
1
vote
1answer
285 views

MySQL Database Design Help?

I am going through my database and what I want to do is re-design it because I feel like it's very messy and that I am doing it wrong. This is just for practice; I've never had anyone teach me so I ...
1
vote
2answers
809 views

Are there any MySQL Triggers or Events that my program can wait for?

Say I want a live feed of emails on a web based email system. Emails are inserted into MySQL tables. Let's say I want my program to know immediately when the table is updated so it can check for new ...
12
votes
1answer
6k views

How to migrate large blob table from mysql to postgresql?

I'm now in process of migrating my MySQL database to PostgreSQL. Almost everything went fine (well, after lots of googling for correct mysqldump params etc.) except one table I have - actually the ...
2
votes
2answers
792 views

Slow Query logging everything

I have a mysql instance that is logging slow queries. I have it set to 1 sec, but I am getting back lots of these:(example) Query_time: 0.000237 Lock_time: 0.000064 Rows_sent: 0 Rows_examined: ...
7
votes
3answers
4k views

query regarding combining an update and an insert query into a single query in mysql

i want to track history of changes for a user, so that whenever he changes his profile, i need to take the old data and store in history and update with new data. I can use a select to get the old ...
11
votes
2answers
4k views

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?
3
votes
2answers
133 views

What would be the best way to model my simple table?

What would be faster: searching for the right row through a table with 17 different columns, each with a tinyint value of 1-4? Or, searching for the right row through a table with only 1 column with ...
2
votes
1answer
3k views

What is the corresponding MySQL TimeStamp in MS SQL Server?

I need a timestamp to be created automatically when I insert information in a table. mySQL has TimeStamp but MS SQL Server TimeStamp doesn’t correspond mySQL. Is there any other way around?