3
votes
2answers
2k views

MySQL on SSD - what are the disadvantages? [closed]

Recently, I heard that I should not host my MySQL database on an SSD drive because there is a big chance of disk failure and data lost. Given that 20% of all queries in my database are INSERTs and ...
7
votes
4answers
31k 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
1k views

Choosing MyISAM over InnoDB for these project requirements; and long term options

Sorry for the long post, but I had to give as much info as possible to make this very vague question more specific. My project's aim is to let users search a (huge) database of variety of products. ...
5
votes
1answer
1k views

Which mysql storage engine to choose?

I'm confused about which mysql engine should I choose (lets talk about the most used : MyISAM and InnoDB). The theories say: Both work with BTree indexes, but MyISAM can work with FULLTEXT index ...
5
votes
1answer
788 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 ...
1
vote
2answers
3k 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 ...
6
votes
3answers
640 views

Issue with composite type in an UPSERT function

I have a function in PostgreSQL 9.1 called fun_test. It has a composite type as input parameter and I keep getting a casting error when I call it. CREATE OR REPLACE FUNCTION netcen.fun_test(myobj ...
6
votes
4answers
7k views

MySQL gives “Out of Memory” error when inserting a large file. From where is this filesize limitation arising?

I'm using a MySQL database to store files. The table I'm using is structured as follows: +--------------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default ...
5
votes
1answer
780 views

will replication from 5.5.20 to 5.0.XX server work?

I gave two machines which run on two entire different versions of MySQL server. I want to do the replication from 5.5.20 to 5.0 server. Will that be possible? Because I remember when I transferred ...
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
2answers
6k views

How to refresh AD security group on Sql Server permissions

I am using Sql Server 2008 on Small Business Server 2003; client is using WinXP. I added a user to my Active Directory Security Group; Why can't this user immediately access the database? It seems ...
4
votes
1answer
4k views

Mysql Master-Master Replication Topologies on >2 machines

I have 3 Mysql servers that I would like to replicate: two (including the main server) are local and one is remote. Let's call my main server A, the secondary server B, and a remote, development ...
3
votes
1answer
1k 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 ...
3
votes
1answer
1k views

FULLTEXT index ignored in BOOLEAN MODE with 'number of words' conditional

fulltext match is ignoring its index when I add a number of words conditional for its boolean mode. The selects are as follows: explain select * from seeds WHERE MATCH(text) AGAINST ("mount ...
2
votes
3answers
289 views

mysql replication master 5.5 slave 5.1 error on create database

I have a replication system where my master has a mysql 5.5 version while the slave is mysql 5.1. I know that this is not supported because the slave version should be greater than the master, but we ...
2
votes
1answer
380 views

row locking within ACID transaction innodb

I have a financial transaction that looks something like this (pseudo): begin select record for update update record(same record as selected) insert another record into another table ...
2
votes
2answers
1k views

How do I determine how much data is being written per day through insert, update and delete operations?

The longevity of SSDs is largely determined by the amount of bytes written by insert, update and delete operations. What is the best way to accurately determine how much data is being written by ...
2
votes
1answer
153 views

Combining columns in index

With reference to RolandoMySQLDBA's answer on MySQL: Index when joining to tables not being used (Performance optimizing question) He mentioned Make sure you build an index that involves the ...
2
votes
2answers
1k 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
1k 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. ...
140
votes
14answers
44k 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 ...
57
votes
5answers
5k views

How can a group track database schema changes?

What version control methodologies help teams of people track database schema changes?
59
votes
6answers
22k 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 ...
60
votes
5answers
7k views

Do stored procedures prevent SQL injection?

Is it true that stored procedures prevent SQL injection attacks against PostgreSQL databases? I did a little research and found out that SQL Server, Oracle and MySQL are not safe against SQL injection ...
31
votes
7answers
16k 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 ...
40
votes
4answers
13k 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 ...
26
votes
3answers
9k views

Parameter Sniffing vs VARIABLES vs Recompile vs OPTIMIZE FOR UNKNOWN

So we had a long running proc causing problems this morning (30 sec + run time). We decided to check to see if parameter sniffing was to blame. So, we rewrote the proc and set the incoming ...
11
votes
5answers
32k views

How to properly kill MySQL?

I have CentOS 64bit with CPanel installed and I use service mysql stop However, it keeps doing ..... for minutes and it never stops. It used to be instant. Any idea why it does that and how to fix? ...
56
votes
5answers
18k 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 ...
20
votes
3answers
37k 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 ...
25
votes
20answers
2k 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 ...
25
votes
8answers
13k 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 ...
12
votes
3answers
18k views

Optimizing queries on a range of timestamps (two columns)

I use postgresql-9.1 with ubuntu 12.04. I need to select records inside a range of time: my table time_limits has two timestamp fields and one property integer. Indeed there are other info columns ...
11
votes
2answers
19k views

Which one is more efficient: select from linked server or insert into linked server?

Suppose I have to export data from one server to another (through linked servers). Which statement will be more efficient? Executing in source server: INSERT INTO ...
14
votes
6answers
13k views

Optimal drive configuration for SQL Server 2008R2

I have a fairly busy database server running SQL Server 2008 R2 that has the following setup: SATA RAID 1 (2 Drives) - OS / Programs SAS RAID 10 (4 Drives) - Sql Database Files (data and logs) SAS ...
30
votes
6answers
3k 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 ...
24
votes
13answers
9k views

How to implement a 'default' flag that can only be set on a single row

For example, with a table similar to this: create table foo(bar int identity, chk char(1) check (chk in('Y', 'N'))); It doesn't matter if the flag is implemented as a char(1), a bit or whatever. I ...
9
votes
5answers
7k views

Survey database design: associate an answer to a user

I'm doing the conceptual model for a survey database. The goal is store the answers given by users (it going to be an Android app). I have three entities: user, question and option. A question will ...
16
votes
7answers
10k views

How can I learn to become a DBA?

Question for you DBAs and such: How do you go about learning the skills to become a DBA without having the 'on hands' or on-the-job training? My experience in DB work has been messing with MySQL via ...
14
votes
1answer
8k views

SQL query for combinations without repetition

I need a query which can be used in (or as) a function and retrieves all combinations of n values. And I need all combinations of length k where k = 1..n. Extended sample input and result so input ...
9
votes
6answers
18k views

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 ...
5
votes
1answer
4k views

Qcache_free_memory not full yet I get alot of Qcache_lowmem_prunes

I just started dabbling with the query cache for our CMS. Can anyone tell me (or at least give a good guess) why I get a lot of Qcache_lowmem_prunes when more than half of Qcache_free_memory is free? ...
18
votes
5answers
4k views

Why use an int as a lookup table's primary key?

I want to know why I should use an int as a lookup table's primary key instead of just using the lookup value as the primary key (which in most cases would be a string). I understand that using a ...
13
votes
3answers
1k views

Why are queries parsed in such a way that disallows the use of column aliases in most clauses?

While trying to write a query, I found out (the hard way) that SQL Server parses WHEREs in a query long before parsing the SELECTs when executing a query. The MSDN docs say that the general logical ...
9
votes
3answers
535 views

What is a deterministic method for evaluating a sensible buffer pool size?

I'm trying to come up with a sane way to understand if the max server memory (mb) setting is appropriate (either should be lower, or higher, or stay the way it is). I am aware that max server memory ...
11
votes
3answers
6k 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 ...
11
votes
1answer
12k views

Performance implications of using OPENQUERY in a view

Please see this question on stackoverflow : I am using an EasySoft ODBC driver to link a SQL Server 2008 R2 Express instance to Interbase and I am having some difficulty with getting metadata ...
7
votes
3answers
8k views

InnoDB table SELECT returns ERROR 2006 (HY000): MySQL server has gone away (after power outage)

This server is a virtual machine running CentOS 6.0, MySQL 5.5.21 There is a database named devSystem. There are InnoDB tables within. Running the following commands causes error ERROR 2006 ...
6
votes
2answers
16k views

SQL Server Transaction Timeout

Is there a way in SQL Server 2008 R2 to cause a timeout for a database modification involving a transaction? We have a scenario where our application code hangs or throws an exception and fails to ...
38
votes
5answers
20k views

Why does ALTER COLUMN to NOT NULL cause massive log file growth?

I have a table with 64m rows taking 4.3 GB on disk for its data. Each row is about 30 bytes of integer columns, plus a variable NVARCHAR(255) column for text. I added a a NULLABLE column with ...

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