Questions tagged [mysql]

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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19
votes
5answers
70k views

Cannot open table mysql/innodb_index_stats [duplicate]

After a fresh install of XAMPP and import from my linux live db that is working to the windows Dev-stage, I started encountering problems with INSERT. Everything else seems to work well. The errors I ...
7
votes
1answer
19k views

Best way to setup master to multi master replication

ORIGINAL QUESTION: I have multiple servers that all need to act as masters, as if one fails the next server kicks in and takes over. I'm just wondering what the best way to replicate is. All servers ...
6
votes
2answers
5k views

Scaling Percona datacenters: setup and replication

Since our startup has taken off nicely we are now meeting with some of those issues that you always assumed would NEVER effect you. We have already scaled alot of our application stack: we offloaded ...
17
votes
4answers
90k views

Call a stored procedure from a trigger

I have created a stored procedure in mysql using the following syntax. DROP PROCEDURE IF EXISTS `sp-set_comment_count`; DELIMITER $$ CREATE PROCEDURE `sp_set-comment_count` (IN _id INT) BEGIN -- ...
5
votes
2answers
9k views

Scheduled optimization of tables in MySQL InnoDB

What is the best way to schedule automatic optimization of tables in a MySQL InnoDB database? Can I use events for example? I have recently had a big performance issue (when querying) with one of the ...
8
votes
2answers
37k views

How can extract the table schema from just the .frm file?

I have extracted the data directory of mysql from a backup and need to get the schema from an old table, however it's a backup from a different machine. I have read a fair number of tutorials today ...
17
votes
3answers
6k 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 count(*)...
15
votes
1answer
14k views

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 message. ...
11
votes
4answers
25k 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 ...
6
votes
1answer
5k views

MySQL upgrade 5.0.88 to the latest version

I have some questions regarding upgrading from 5.0.88 to the latest version. Why should I upgrade? If so, which version should I consider? What are all the known risks? Is upgrading step by step ...
8
votes
3answers
7k views

Changed max_allowed_packet and still receiving 'Packet Too Large' error

I use mysqldump to create a flat file for backup purposes. I have used this file to recreate the database on an alternate server. I ran the import process through ssh on the command line and I ...
4
votes
3answers
6k views

MySQL slow log configuration

Is there a way of making MySQL slow logs to start new log file every day ? At the moment its just a single large file, and have to grep lines for every day. It would be much more convenient to have ...
5
votes
1answer
3k views

How does max_allowed_packet affect the backup and restore of a database?

I have a database based on mysql 5.0.75-0Ubuntu10.2, running under Ubuntu 9.04. I have a table in that database with a medium blob column. I have been using automysqlbackup to do nightly backups/dumps ...
3
votes
1answer
2k views

query cache hit value is not changing in my database

The query cache hit value is not changing in my database only for some queries.If I write select * from drugs_info limit 1000; the query cache hit has changed, but if I execute the following ...
2
votes
1answer
838 views

mysql directory grow to 246G after one query, which failed due to table is full

I was trying to run the following statement with the hope to create a join of two existing tables. create table CRS_PAIR select concat_ws(',', a.TESTING_ID, b.TRAINING_ID, a.TESTING_C) as k, ...
68
votes
5answers
11k views

How can a group track database schema changes?

What version control methodologies help teams of people track database schema changes?
26
votes
2answers
24k views

MySQL - varchar length and performance

Is declaring VARCHAR size make sense for performance? Is there any difference (in speed) between VARCHAR(50) and VARCHAR(255)? Or defining length is logic/design constraint?
9
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3answers
30k views

Why do MySQL tables crash? How do I prevent it?

I'm the Administrator of a Moodle site which had its Users table corrupted and it became unusable. Luckily, a simple REPAIR TABLE mdl_user made it work back again. The thing is that I don't know why ...
7
votes
1answer
10k views

Best solution for cross-datacenter MySQL master-slave replication

We are working on a new system architecture for our company. We have a HPC, which runs in our own data-center and we are planning our front-end and a fallback system on Amazon Web Service. System ...
5
votes
1answer
5k views

Proper tuning for 30GB InnoDB table on server with 48GB RAM

I have a 30GB 15M rows InnoDB MySQL 5.5.15 table. It is running on a server with many other MyISAM tables (300GB db). The system has 48GB RAM. Besides the default configurations, I've changed the ...
18
votes
2answers
2k views

What can we do in MySQL 5.0 Replication to address bandwidth concerns?

I am developing an application to run on the client PC (Win) which is configured with a MySQL server 5.1 instance that will act as read-only slave to the remote master. The remote master has dozens of ...
6
votes
1answer
13k views

Any known issues upgrading from MySQL 5.1.73 to 5.6.21?

I am planning my MySQL DB ver5.1.73 running on a CentOS 6.5 machine to MySQL 5.6.21. I understand the basic procedure for this based on what I have read on StackOverflow, but I was curious if anyone ...
14
votes
3answers
28k views

Why does MySQL ignore the index even on force for this order by?

I run an EXPLAIN: mysql> explain select last_name from employees order by last_name; +----+-------------+-----------+------+---------------+------+---------+------+-------+----------------+ | ...
11
votes
2answers
6k views

Any gotchas at all with converting from MyISAM to InnoDB?

I'm ready to move from MyISAM to InnoDB but wanted to know if there was a full list of things to look for? For example, I haven't seen any list mention that running DISABLE KEYS on an InnoDB table ...
13
votes
3answers
6k 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 ...
9
votes
2answers
7k views

Is this a normal set of MySQL privileges?

Using phpmyadmin on a local test wamp setup, and well as pretty much the title states, there are 3 users marked as user = ANY, password = NO, such as: USER | HOST | Password | Global Priv | Grant -...
8
votes
2answers
8k views

Is it bad to create many mysql temporary tables simultaneously?

I need to make heavy statistical analysis to deliver some data to users. Currently, I catch the data from mysql and process them via PHP arrays. However, mysql temporary tables are quite better (...
6
votes
4answers
21k views

Single slave - multiple master MySQL replication

I need to replicate different MySQL databases from multiple servers into a single slave server. How can this be done? is there a way to define multiple master hosts?
2
votes
2answers
6k views

Stress test MySQL with queries captured with general log in MySQL

Is there any tool available which can do stress testing using the log file created by MySQL general log? After a lot of search on google I found few stress testing tools which only use some benchmarks ...
8
votes
1answer
1k views

Does MySQL still handle indexes in this way?

Dropping a duplicate index in MySQL was taking rather long, so while I was waiting I searched about it & found this post from 2006, talking about how MySQL handles ADD and DROP index. If a ...
8
votes
1answer
3k views

Can I have an InnoDB master and MyISAM slaves with Full-Text for searching?

I'd like to use InnoDB on the master, for its transactional ability, but MyISAM on the slaves for the full-text search ability. Is this possible?
8
votes
2answers
1k views

Advice on a basic design, first time database design

I am taking a course to become a Java developer. The course involves using databases but we never really design any, unfortunately. Most of the time we get pre-made databases and we have to ...
6
votes
4answers
16k views

Benefits of BTREE in MySQL

What are the pros and cons of using a BTREE index in MySQL, regarding query speed, disk storage and memory usage? Does BTREE provide easier iteration in increasing order ? What kind of queries would ...
6
votes
1answer
2k views

“Site Offline” MySQL server failing to start and stop

I'm hosting a few sites on linode and have encountered a strange problem. For the last two years the site has been running perfectly fine, and now randomly all the websites on the server go to the "...
84
votes
6answers
139k views

Safest way to perform mysqldump on a live system with active reads and writes?

I'm not sure if this is true but I remember reading if you run the following command in linux mysqldump -u username -p database_name > backup_db.sql while reads and writes are being made to a ...
20
votes
2answers
28k views

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 ...
31
votes
5answers
90k views

How to properly kill MySQL?

I have CentOS 64bit with CPanel installed and I use: service mysql stop It just keeps ticking periods and never seems like it stops. In the logs it just posts a lot of: 130303 17:42:38 [Warning] /...
38
votes
2answers
70k views

selecting where two columns are in a set

This might be a silly question, and my suspicion is that I can't do this, but is there a construct in SQL that would allow me to do something like the following: SELECT whatever WHERE col1,col2 IN ((...
23
votes
8answers
54k views

Any option for mysqldump to ignore databases for backup?

We have 40 databases in our server. We want to take 36 databases backup using mysqldump. How can i ignore remaining 4 databases in mysqldump command? Is there any option for mysqldump to ignore ...
22
votes
7answers
57k views

Need to migrate SQL Server to MySQL

I have a database on SQL Server 2008 on a Windows server and I want to move all of the data to a MySQL database on a Ubuntu server. I have tried using the SQL Server Import and Export Wizard with the ...
10
votes
3answers
53k views

Restoring MySQL Tables from .ibd, .frm and mysqllogbin files

For some reason, when I try to open up my tables that are stored in .frm and .ibd files (whether on MySQL or phpmyadmin) it gives me a syntax error, or it says it does not exist. I've read the other ...
5
votes
2answers
9k views

When should I think about upgrading our RDS MySQL instance based on memory usage?

It seems like our DB server is doing garbage collection at a increasingly faster rate, which seem normal since it's growing. What's a good rule of thumb of when to switch to a bigger instance, I'm not ...
11
votes
2answers
12k views

Performance of a Trigger vs Stored Procedure in MySQL

A post here on DBA.StackExchange (What are the best practices for triggers to maintain a revision number on records?) has spawned an interesting question (at least, interesting to me) regarding ...
4
votes
1answer
6k views

Mysql Memory table getting many locks

On my site I log every pageview (date, ip, referrer, page, etc) in a simple mysql table. This table has the following activity: 1 SELECT per minute 1 DELETE per minute no UPDATE queries Lots of ...
30
votes
1answer
52k views

INT(5) vs SMALLINT(5): numbers in parenthesis after the numeric type

In MySQL table definitions is there a different between INT(5) and SMALLINT(5)? Or do they both represent the same size?
8
votes
2answers
3k views

Insert-heavy InnoDB table won't use all my CPU

I have a packet log database, which is almost never queried. It just needs to be fast on inserts. I'm using InnoDB because I'd like to maintain ACID compliance, since even losing a single packet could ...
11
votes
3answers
18k views

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 ...
6
votes
3answers
20k views

Disable trigger for just one table

Is it possible to disable a trigger momentarily but for just one table. For example I have table, TableA with an on insert, update and delete trigger. I also have a table B with the same triggers but ...
5
votes
1answer
1k views

Should I use a storage engine other than MyISAM to optimise these tables or should I get better disks?

There's a production database I'm working on, whose 4 largest tables contain between 4 million and 10 million rows each and about 15 fields each, with indexes on different field types (numbers, ...
4
votes
4answers
15k views

Optimized my.cnf for high-end and busy server

Curretly my main culprit of poor performance is MySQL and I'm not a DB savvy. So far, I've had little luck in optimizing mysql configs on my server, which has a Sandy Bridge processor with 16GB ram ...

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