54
votes
5answers
3k views

How can a group track database schema changes?

What version control methodologies help teams of people track database schema changes?
49
votes
6answers
14k views

What are the differences between NoSQL and a traditional RDBMS?

What are the differences between NoSQL and a traditional RDBMS? Over the last few months, NoSQL has been frequently mentioned in the technical news. What are its most significant features relative to ...
32
votes
4answers
12k views

What are Objective Business Reasons to Prefer SQL Server 2012 over 2008 R2?

My company is facing the decision whether to purchase SQL Server 2012 Denali or SQL Server 2008 R2 for a new database server. I am looking for objective reasons to choose one over the other. Our ...
25
votes
7answers
8k views

Writing a simple bank schema: How should I keep my balances in sync with their transaction history?

I am writing the schema for a simple bank database. Here are the basic specifications: The database will store transactions against a user and currency. Every user has one balance per currency, so ...
52
votes
8answers
4k views

Does SQL Server read all of a COALESCE function even if the first argument is not NULL?

I'm using a T-SQL COALESCE function where the first argument will not be null on about 95% of the times it is ran. If the first argument is NULL, the second argument is quite a lengthy process: ...
17
votes
3answers
23k views

How to find out who deleted some data SQL Server

My boss had a query from a customer yesterday asking how they could find out who deleted some data in their SQL Server database (it is the express edition if that matters). I thought this could be ...
23
votes
8answers
7k views

Tool to generate large datasets of test data [closed]

Many times when trying to come up with an efficient database design the best course of action is to build two sample databases, fill them with data, and run some queries against them to see which one ...
24
votes
20answers
1k views

How to dive into an ugly database?

I'm sure many of you are/were dealing with a ugly database. You know, that database that isn't normalized at all, that database where you have to do a large painfully query to get the most trivial ...
9
votes
3answers
10k views

Why is 'LOAD DATA INFILE' faster than normal INSERT statements?

I've read an article that mentioned we can achieve 60,000 inserts per second by LOAD DATA IN FILE statement that read from csv files and insert it into database. Why should it differ from normal ...
33
votes
5answers
10k views

When should I use a unique constraint instead of a unique index?

When I want a column to have distinct values, I can either use a constraint create table t1( id int primary key, code varchar(10) unique NULL ); go or I can use a unique index create table t2( id ...
29
votes
7answers
2k views

The smallest backup possible … with SQL Server

Daily we ship our SQL Server backups across the WAN. We need to minimize the size of these backups so it does not take forever. We don't mind if our backup process takes a bit longer; as it stands ...
20
votes
1answer
4k views

Designing a platform: one database or multiple databases?

We are building a web platform that incorporates multiple services, each with its own underlying data. These services are being built independently following the principles of Service-Oriented ...
17
votes
1answer
17k views

intermittent MySQL crashes with error “Fatal error: cannot allocate memory for the buffer pool”

Added on edit, 2013-05-29: Because this is a long question and discussion, here's a short summary of the question and the solution. I had problems running MySQL and Apache on a small Linux server (1 ...
13
votes
3answers
14k views

Is it safe to use innodb_flush_log_at_trx_commit = 2

I turned innodb_flush_log_at_trx_commit = 2 and get a very fast write speed. But is it safe be used in production web site?
17
votes
3answers
10k views

PostgreSQL multi-column unique constraint and NULL values

I have a table like the following: create table my_table ( id int8 not null, id_A int8 not null, id_B int8 not null, id_C int8 null, constraint pk_my_table primary key (id), constraint ...
15
votes
3answers
813 views

difference in execution plans on UAT and PROD server

I want to understand why there would be such a huge difference in execution of the same query on UAT (runs in 3 sec) vs PROD (run in 23 secs). Both UAT and PROD are having exactly data and indexes. ...
11
votes
7answers
13k views

Is it possible to mysqldump a subset of a database required to reproduce a query?

Background I would like to provide the subset of my database required to reproduce a select query. My goal is to make my computational workflow reproducible (as in reproducible research). Question ...
11
votes
3answers
4k views

SQL Server 2008 R2 “Ghost Memory”?

We have a dedicated SQL Server 2008 R2 machine that is experiencing some strange memory issues.. The machine itself has plenty of resources including two quad-core processors, 16gb of RAM and 64bit ...
5
votes
1answer
3k 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 ...
4
votes
2answers
3k 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 ...
8
votes
2answers
5k views

Why index REBUILD does not reduce index fragmentatation?

I have used ALTER INDEX REBUILD to remove index fragmentation. In some cases REBUILD does not seem to remove this fragmentation. What are the reasons why REBUILD does not remove fragmentation? It ...
6
votes
1answer
2k views

How large will a MySQL database be relative to the dump file?

I'm restoring a ~52GB dump to a MySQL database. The ibdata1 file has already exceeded the size of the dump file and the restore is still incomplete. Is there any way to estimate the final size of the ...
6
votes
1answer
2k views

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 ...
6
votes
4answers
3k views

MySQL Replication - Introduce new Slave to replication

I've recently taken on a sys admin position managing a group of 20 (or so) servers. One thing I haven't dealt with before (apart from in a test situation), is introducing a new slave to the MySQL ...
5
votes
1answer
7k views

Performance implications of using OPENQUERY in a view

Please see this http://stackoverflow.com/questions/7753380/performance-implications-for-using-openquery-in-a-view question on stackoverflow, it's a cross over subject and would love a dba's POV
3
votes
1answer
4k views

Fixing tables out of sync as reported by pt-table-checksum, pt-table-sync is not working

I have several tables being reported by pt-table-checksum with CRC_DIFF between my master and slave servers using the following commands: $ pt-table-checksum h=master,u=user,p=password ...
3
votes
3answers
630 views

Restoring an old backup to latest MySQL release

Our old database is MySQL 5.1 server and is four years old. If I uninstall MySQL 5.1 Server and install the latest release and restore the backup, will I gain performance benefits? I guess the new ...
16
votes
4answers
2k views

Is 'Avoid creating a clustered index based on an incrementing key' a myth from SQL Server 2000 days?

Our databases consist of lots of tables, most of them using an integer surrogate key as a primary key. About half of these primary keys are on identity columns. The database development started in ...
6
votes
4answers
2k views

One slave, multiple masters MySql

Is it possible to set-up MySql Replication to have one slave listening to two different masters?
5
votes
1answer
1k views

Find transactions that are filling up the version store

we have enabled the "READ_COMMITTED_SNAPSHOT" for some of our SQL Server 2005 databases. Now from time to time we see that our TempDB is filling up the harddisk and we suspect the version store to be ...
4
votes
2answers
2k 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 ...
4
votes
4answers
2k views

Is raid 5 suitable for a mysql installation?

Is raid 5 suitable for a mysql installation? Let me explain my application further. My application is a socket programming which will connect with gps device to receive gps string and there after do ...
4
votes
1answer
5k views

How to setup replication(Master/slave) in MySQL 5.5.20?

I have two servers both running on MySQL 5.5.20 and I want to setup replication, so every update/insert on Master would reflect immediately on Slave machine. I tried following this tutorial (I used ...
3
votes
3answers
3k views

Can I specify a different disk for a specific MySQL table?

I use my home machine as my personal database for my hobby analytics project. This machine has an SSD for the main drive where MySQL stores its data. It also has a secondary hard drive that is ...
2
votes
2answers
576 views

Mysql database replication on different vlan/subnet/another site

Saw the posts for "MySQL high availability, failover and replication with Latency" Is it possible to work it in a DR site when its not in the same vlan?
11
votes
1answer
1k views

DELETE vs TRUNCATE

I am trying to get a greater understanding on the differences between the DELETE and TRUNCATE commands. My understanding of the internals goes something along the lines of: DELETE -> the database ...
5
votes
2answers
1k views

ORA-04031: unable to allocate bytes of shared memory (“”,“”,“”,“”)

I am receiving this error in a development database. It happens on some specific queries (simple inserts and deletes via .NET application). The database is used by one user, and error happens ...
5
votes
1answer
1k views

MySQL Replication : 1 Slave / Multiple Masters

I have a web app with 2 web servers and 2 database servers. The DBs are setup for multimaster replication. (this is the primary environment) I also have the exact same setup on a different location ...
4
votes
3answers
2k 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 ...
3
votes
2answers
934 views

Quick MySQL Backup

I have a database which is grown to 3GB and it has 3 MyISAM tables. And I have 4GB RAM. What will be the best (quick) way to backup this database without any performance lack. Or mysqldump will work ...
3
votes
3answers
478 views

Dynamically changeable database

We have a database and some data is stored in a Trucrypt folder, my question is how can I include this trucrypt folder. The data type is MyISAM. I saw there is a symbolic link, but not really clear ...
2
votes
2answers
664 views

Which first: upgrade mysql version or convert storage engine?

I inherited a production mysql server at 5.0. It uses MyISAM exclusively. It is not a high volume database but it does have some large datasets. I am planning on: upgrading to 5.5 converting ...
2
votes
1answer
565 views

Create a custom log table in MySQL

Is it possible to create a custom log table. For example I have 10 schema and I would like to log if somebody is using the "areva" schema. I want to know the last executed command time and the user. ...
2
votes
1answer
619 views

MySQL Cluster — Storing table data on data nodes

I have setup MySQL Cluster with the MySQL server node and the Management node on a single server, and 2 data nodes (each on a different server for 3 servers in all). After installing, I run ndb_mgm ...
2
votes
2answers
1k views

Preventing mysql deadlocks in your php application that uses SELECT… LOCK IN SHARE MODE

If I understand SELECT ... LOCK IN SHARE MODE correctly, you can place it into a mysql transaction to select the rows you will be working with during that transaction. This is done in order to "lock ...
1
vote
1answer
2k views

gain admin access to sql express 2008

I have inherited a Windows 7 Professional pc with an existing instance of SQL Express 2008. I have local admin rights on the machine. I do not know the SA password. I am unable to create databases or ...
1
vote
1answer
451 views

Removing/overwriting sensitive data located in already deleted records in ibdata files

As far as I know, using InnoDB tables with innodb_file_per_table = off does not prevent deleted data from being visible in the ibdata1 file. I know this is by-design, and that I could switch the ...
1
vote
1answer
659 views

decreased performance of stored procedure when migrated from mysql server 5.0 to 5.5

i recently testing the move of our db from one server to another. as part of this process i copied all the data to the new db and started testing it. as a comparison i run a store procedure whose ...
1
vote
1answer
682 views

Secure method beside phpMyAdmin for remote mysql

Recently, one of my centos linux servers was hacked and the cause of due to phpMyAdmin. It was said due to this problem PhpMyAdmin vulnerability CVE-2011-2505 ...
113
votes
14answers
23k views

How do you document your databases?

I find that most of my clients are not documenting their databases at all and I find that pretty scary. To introduce some better practice I would like to know what tools/process you are using. How ...

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