3
votes
2answers
10k views

MySQL Error Reading Communication Packets

In MySQL error logs, I see these quite few a warnings like these: 120611 16:12:30 [Warning] Aborted connection 2619503 to db: 'db_name' user: 'user_name' host: 'webapp_hostname' (Got an error reading ...
8
votes
3answers
501 views

Where to start with Oracle?

This question only needs one answer: a list of great resources for getting started with Oracle, including Database Administration, PL/SQL and SQL. You may find your question has been closed as a ...
12
votes
2answers
650 views

Decision criteria on when to use a non-dbo schema vs a new Database

I'm mostly an application developer but find myself having to do all the up-front database work for my current project (btw... its MS SQL Server 2008). As a first decision, I'm trying to figure out ...
9
votes
2answers
1k views

Do natural keys provide higher or lower performance in SQL Server than surrogate integer keys?

I'm a fan of surrogate keys. There is a risk my findings are confirmation biased. Many questions I've seen both here and at http://stackoverflow.com use natural keys instead of surrogate keys based ...
8
votes
4answers
9k 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 ...
7
votes
2answers
5k 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
2answers
4k views

Multicolumn index and performance

I have a table with a multicolumn index, and I have doubts about the proper sorting of the indexes to get the maximum performance on the queries. The scenario: PostgreSQL 8.4, table with about 1MM ...
4
votes
3answers
3k 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 ...
8
votes
1answer
2k 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 ...
6
votes
2answers
4k 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 ...
5
votes
1answer
4k views

Many to Many and Weak Entities

I have an entity that cannot exist without being defined by another, and I want this entity to participate in a many-to-many relationship. Example: An artist has an album (the album cannot exist ...
3
votes
1answer
4k 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 ...
6
votes
2answers
375 views

Help with this query

I have a person table. I also have a car table and books table. The car and book table both have a foreign key back person. I am trying to count the number of books and cars each person has: I try: ...
5
votes
1answer
521 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 ...
5
votes
1answer
961 views

MySQL EXPLAIN doesn't show 'use index' for FULLTEXT

I have a basic table : create table fullTextTest ( id INT(11) NOT NULL, superText CHAR(255) NOT NULL, superLongText TEXT NOT NULL, primary key (`id`), FULLTEXT KEY `superText` ...
5
votes
3answers
3k views

Why is SSMS inserting new rows at the top of a table not the bottom?

Whenever I manually insert a row into a table in SQL Server Management Studio 2008 (the database is SQL Server 2005) my new row appears at the TOP of the list rather than the bottom. I'm using ...
2
votes
1answer
2k views

MySQL upgrade 5.0.88 to latest

Very interesting and informative blog.. I have a question - i have a requirement of upgrading from 5.0.88 to latest version.. Why should i upgrade? if so, which version should i consider? What ...
1
vote
1answer
4k views

ERROR 1114 (HY000) at line 6308 in file & The table user_analysis is full

There is a SAN mounted 1TB partition for Mysql backups in our server with version 5.0.45-log. From two days, im seeing the log entries ERROR 1114 (HY000) at line 6308 in file & The table ...
37
votes
6answers
35k views

What are the main causes of deadlocks and can they be prevented?

Recently one of our ASP.NET applications displayed a database deadlock error and I was requested to check and fix the error. I managed to find the cause of the deadlock was a stored procedure that was ...
13
votes
7answers
25k views

Get the rank of a user in a score table

I have a very simple MySQL table where I save highscores. It looks like that: Id Name Score So far so good. The question is: How do I get what's a users rank? For example, I have a users ...
25
votes
3answers
25k 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?
14
votes
7answers
23k 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 ...
59
votes
8answers
5k 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: ...
25
votes
1answer
30k 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 ...
18
votes
1answer
25k views

Optimal way to ignore duplicate inserts? [duplicate]

Background This problem relates to ignoring duplicate inserts using PostgreSQL 9.2 or greater. The reason I ask is because of this code: -- Ignores duplicates. INSERT INTO db_table ...
16
votes
7answers
44k 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 ...
11
votes
3answers
15k 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 ...
18
votes
1answer
24k views

How do I attach a database in SQL Server?

Some common questions relating to attaching databases in SQL Server: What does it mean to attach or detach a database? How do I detach a database? How do I attach a database? What ...
20
votes
4answers
7k views

Using SQL Profiler on a database that's in production

As a developer, I use SQL Profiler quite often. It's a good debugging tool, both to track what my code is doing and to analyse performance problems. But I've always used it on my development ...
9
votes
2answers
5k views

How to create an Event Notification that runs a Job/procedure when mirroring state changes

I'm asking this question in the sequence of this one Can I send a string over TCP using T-SQL? Remus Rusanu exposes what it seems to be an optimal solution for my problem, but... I'm too immature to ...
4
votes
1answer
2k 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 ...
15
votes
4answers
15k views

Aggressive Autovacuum on PostgreSQL

I'm trying to get PostgreSQL to aggressively auto vacuum my database. I've currently configured auto vacuum as follows: autovacuum_vacuum_cost_delay = 0 #Turn off cost based vacuum ...
13
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
3answers
6k views

Should I add an arbitrary length limit to VARCHAR columns?

According to PostgreSQL's docs, there's no performance difference between VARCHAR, VARCHAR(n) and TEXT. Should I add an arbitrary length limit to a name or address column?
5
votes
1answer
4k 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
709 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
1answer
3k 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 ...
16
votes
4answers
35k views

Logical operators OR AND in condition and order of conditions in WHERE

Let's examine these two statements: IF (CONDITION 1) OR (CONDITION 2) ... IF (CONDITION 3) AND (CONDITION 4) ... If CONDITION 1 is TRUE, will CONDITION 2 be checked? If CONDITION 3 is FALSE, will ...
8
votes
3answers
13k 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 ...
4
votes
2answers
5k 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 ...
4
votes
4answers
11k 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 ...
16
votes
1answer
6k 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 ...
14
votes
3answers
11k views

Is it possible to restore sql-server bak and shrink the log at the same time?

We have a bak file from a client that we have transferred to our developer offices for problem investigation. The backup is currently 25GB and the restored database is about the same size however it ...
13
votes
2answers
10k 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 ...
10
votes
2answers
777 views

Postgres query plan of a UDF invocation written in pgpsql

It's possible when using the pgadmin or plsql to get a hold of a query plan for a sql statement executed via a UDF (using EXPLAIN). So, how do I get a hold of the query plan for a particular ...
10
votes
1answer
4k views

Deadlock error isn't returning the deadlock SQL

Transaction (Process ID) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction. I am getting this error randomly when one of my ...
6
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 ...
5
votes
3answers
5k 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 ...
4
votes
3answers
1k views

Log MySQL DB changing queries and users

For security reasons I need a server-side (running Debian 6.0 Squeeze) logging of all queries that may have changed the content of a MySQL DB (v. 5.1) and the user who issued it. I had to rule out ...
4
votes
2answers
7k views

MySQL Event does not run

i am running mysql 5.1.41 that came bundled with xampp on windows. the problem is that the event doesnt run automatically even when the event scheduler is ON. i have a table named ta_table using ...

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