MySQL 5.1 : The Second Major Release of MySQL 5

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MySQL: Moving Database from Windows to Linux

I have a Windows based dedicated server have below configuration: Windows edition: Windows Server 2008 R2 Standard Service Pack 1 Processor: Intel(R) Xeon(R) CPU X5460 @3.16GHZ 3.16 GHZ (2 ...
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MySQL Server constantly crashes

my apologies for having already posted on this issue, but it has moved on so far I feel a new question is the only way to go. First a little history - I have a MySQL server which runs a few small ...
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1answer
141 views

Merge difference MySQL DBs into a single new server

I have 4 servers which has it's own MySQL server along with databases and users. Now we have a new server dedicated only for MySQL and we would like to merge those MySQL servers into this new one. ...
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28 views

On replicating all tables of a given database except for those starting with some pattern

I'd like a slave to replicate all tables of a given database except for those starting with some pattern, eg. those with names starting with 'nc' (non-critical, redundant denormalized tables). So I ...
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134 views

Best way to select rows containing a substring

I've a table named comments where comment is a field where comment will be stored. Now I want to find -1 within that comment. the -1 should be independent. That is, it should not be joined with ...
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1answer
171 views

MySQL: Different thread states in Query execution

My MySQL 5.1 bases Intranet system is facing very bad performance during high load. When observe through MonYog, I found below thread states: We can simply understand the different thread state by ...
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2answers
308 views

MySQL views and table locking (5.1 MyISAM)

I have a large (160 million rows, 50GB) table in MySQL 5.1 using MyISAM. If I were to construct a view defined by a fairly complicated query, would a SELECT on the view lock the underlying table?
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2answers
123 views

Mysql select ends with 'killed'

Okay, I'm sure this will turn out to be something dumb, but then I'm a dumb n00b DBA. I've got a largish table, about 163 million rows and something like 44 GiB. After some experiments with ...
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66 views

MySQL: Sometimes query failed to use index

I have a complex query including join of 4-5 tables. 1 months back, I have optimized this query and it was using the index. Also, two months back, index of all tables had been rebuilt by just export ...
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1answer
44 views

MySQL: Algebra in Union operation

I have below query: select entity_id from table1 exc UNION select entity_id from tabl2 inc On execution, I got 24419 rows. When I execute select entity_id from table1 exc I got 16235 rows and on ...
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1answer
361 views

The total number of locks exceeds the lock table size, even after increasing buffer pool size

I am trying to partition a table with 200 million records in it. This table already exists: CREATE TABLE linkmap_ntoken ( target_nToken varchar(200) NOT NULL, ntoken_hashcode int(15) NOT NULL, ...
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1answer
142 views

MySQL: What is SQL mode and why we use it

If in an application, if we execute sql_mode=mysql4.0 as a first query in my application but using MySQL 5.1 in my application then what will happen? Will my system use MySQL 4.0 or MySQL 5.1 ...
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29 views

MySQL: why provide size of a datatype in table definition? [duplicate]

Below is an example table definition: CREATE TABLE IF NOT EXISTS `mytable` ( `id` MEDIUMINT(5) NOT NULL AUTO_INCREMENT, `title` varchar(255) DEFAULT NULL DEFAULT '', `content` text ...
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1answer
2k views

statistics State in MySQL Processlist

I have a busy MySQL Server having query SELECT sys_sess_state, index_state, timeout_lvl, last_queued_dt, last_polled_wait_dt, create_id, create_dt, modify_id, modify_dt FROM PQR_AM_SYSTEM_SESSION ...
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1answer
189 views

MySQL: What is the most optimized way to use datetime type field in query

I am working on optimization of some slow queries in my application. I found a query in which datetime comparison has been used. Below is the subquery: select * from jos_content c where c.visible = 1 ...
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16 views

MySQL: How logging is useful in performance improvement

My application is facing performance hit. Its a MySQL-5.1.55 version. I am using Windows 2008 dedicated server with 8 GB for the database. There is only one database in this whole system. Till now, I ...
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0answers
32 views

MySQL: system variables and status variables related with Disk I/O

How disk I/O is related with MySQL performance improvement. I have a MySQL-5.1.58 based Intranet application equipped with Windows 2008 server and 8 GB RAM. Even, When my application face performance ...
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2answers
473 views

MySQL: why assign NULL as default value

When we define a table, multiple times we assign default value of a column as NULL. I have How NULL is different than empty value('') as well as 0? Is there any impact of NULL value in query ...
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143 views

MySQL: how to determine key_len and its role in performance improvement of a query

I have a query, below is the structure of the table: CREATE TABLE `jos_tag_rules_fields` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL DEFAULT '', `label` varchar(255) ...
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2answers
60 views

MySQL using swap during conversion to InnoDB

I'm trying to convert some MyISAM tables in my database to InnoDB (MySQL 5.1). The server has quite a bit of memory (96G), and the tables that are giving me problems can be on the order of 50 millions ...
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1answer
41 views

Tracking changes on a replication slave

I suspect the answer to this is "you're boned", but I'd like to see if there are any good options that I haven't explored. We're building a system that will integrate with a 3rd-party POS system and ...
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177 views

MySQL: How to get locked tables list at a time

Is there any way or any query exist in mysql which list down all the locked tables at a time. I have dedicated Windows 2008 DB server with 8GB memory. In my MySQL5.1 based application, suddenly we get ...
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4answers
5k views

Why use WHERE 1 or WHERE 1=1?

Usually, if conditions are not required in our query statements, we don't use a WHERE clause. But I see a WHERE 1 clause being used in many places, even where other conditions are not present. Why ...
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1answer
110 views

MySQL: fetch multiple global status and system variable in a single query

When we execute SHOW global status; or SHOW variables; we get list of 291 and 278 records in the resultset. For performance perspective, only few of them are much important. I have to fetch these ...
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160 views

MySQl: slow query is not using index in joining

Below is the configuration of my DB server: Apache version : Apache/2.2.22 (Win32) mod_ssl/2.2.22 OpenSSL/0.9.8 PHP version : 5.3.13 MySQL version : mysqlnd 5.1.11 Windows Server 2008 Standard ...
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1answer
95 views

Help interpreting a MySQL execution plan

I'm trying to understand a slow query. The SELECT has been running (at this moment) for almost 18000 seconds (output from a SELECT on PROCESSLIST): id: 22 time: 17870 ...
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858 views

Difference between show status and show global status in mysql

When I execute "show status" and "show global status" in MySQL at interval of 5 seconds , I got set of 291 results each time. But, value of some parameters are different. Below are the list of those ...
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1answer
101 views

How big is a tmp table?

I've got an RDF table in MySQL 5.1 with the MyISAM engine. Here's the table definition: CREATE TABLE `node` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `graph` varchar(100) CHARACTER SET latin1 ...
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1answer
348 views

TCP sockets bottleneck with InnoDB/Debian?

We have a big mysql performance issue on a production environment with 18 "front" servers sending mysql queries to a unique mysql server. We are using Redis on each front server for a number of ...
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62 views

Understanding how MySQL indexes work

I'm reading this page but I can't get past the following parts: When all tables are processed, MySQL outputs the selected columns and backtracks through the table list until a table is found ...
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834 views

MySQL: High sort_buffer_size setting value

Thing is I was getting plenty of 131104 20:10:36 [ERROR] /usr/sbin/mysqld: Sort aborted with 256M and rather erratic behaviour in my load test. Now at sort_buffer_size = 1024M ...
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2k views

MySQL temporary column in SELECT statement

I'd like to do some calculations in a MySQL query. I've created some temporary columns which I'd like to use for the calculation. SQL fiddle for currently working (but discouraged) SQL query: ...
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344 views

mysql 5.1 — unknown variable 'basedir=c:/mysql/'

I recently changed the default port(3306) to another for mysql. I did it by changing the my.ini file and did restart of the server. No other changes were made whatsoever. When connecting using a GUI ...
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1answer
55 views

query not taking index into account

EXPLAIN EXTENDED SELECT SQL_CALC_FOUND_ROWS SQL_NO_CACHE g.*, u.user_id FROM geotable g JOIN userstable u ON g.uid = u.uid -- corners selection: WHERE (lat BETWEEN ? and ? AND lon ...
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1answer
2k views

Selecting multiple columns from multiple rows in one column (subquery?)

I'm working with MySQL 5.1.68. I have a situation where I'd like to select rows from another table into a column. I'd like to output this: id # name # citizen_name (multiple citizen names) 1 # ...
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1answer
3k views

mysql trigger to insert/update date column from datetime column

probably simple question but can't get it to work: I have a table with two datetime columns. In order to set up a date index and have simpler queries, i have added two date columns next to them. ...
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Accidentally I had deleted a database from production server working with MySQL

I have its backup as a full and an incremental backup took using enterprise backup. Is it possible to restore a specific database or else what should I do as an immediate action?
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1answer
517 views

UPDATE SET REPLACE() matches but does not change

I've seen another post about this exact thing but it's 1-1/2 years old so I thought I'd make my own...besides, the other post did not help me. What I am trying to do is pretty straight-forward. To ...
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1answer
66 views

mysql's query cache behaviour on LIMIT

Is it accurate to assume that MySQL's query cache gets checked on subsequent execution of queries in the form SELECT ... WHERE ... LIMIT x, y where the the only varying paramaters in the query are x ...
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1answer
251 views

Out-of-Range and Overflow Handling for float values

am using mysql 5.5 log version with sqlmode='' .I have many columns with float(9,3) as the type. Say for ex one column taxvalue (9,3) Currently if the user enter the value above 999999.000 MYSQL ...
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1answer
197 views

Why would one use the Innodb Plugin instead of the builtin Innodb in Mysql 5.1? (GPL)

Innodb works in Mysql 5.1 whether or not the innodb plugin, ha_innodb_plugin.so is loaded at startup or not. Configuration dependent of course. What are the advantages and disadvantages of either ...
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205 views

Index for ORDER BY on aggregate in MySQL

I'm working with the following query: SELECT *, SUM(entries_count) AS entries_count FROM leads WHERE promo_id IN (1, 2, 3) GROUP BY user_id ORDER BY entries_count DESC LIMIT 25 OFFSET 100; It's ...
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1answer
481 views

Why does max_connections in my.ini not match concurrent connections in Mysql instance config wizard?

MySQL 5.1.x | Windows Server 2003 Can someone please clarify why max_connections in my.ini is much larger than the manual value I specify in the Concurrent Connections Dialogue? For example, if I ...
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2answers
40 views

Calculating the number of times a group occures

I'm trying to figure out how many times in my database a particular grouping has occurred. I have two relevant tables. mysql> describe logins; ...
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1answer
112 views

Upgrading MySQL 5.1 to 5.5 - All tables gone [closed]

I'm trying to upgrade from MySQL 5.1 to MySQL 5.5. I followed the instructions here: http://dev.mysql.com/doc/refman/5.5/en/windows-upgrading.html I also adjusted the Datadir. But after the upgrade, ...
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80 views

Best way to handle temporary data

Say I have a table prices. Users can see the prices of this table (I'm simplifying it). Users also can send prices to the server, so the server is going to collect these data in another table ...
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52 views

Conditional Counting

I'm analyzing a database of login records for a university and I'm trying to write a query that will give me an idea as to how many users are using the labs for short bursts, verse a more extended ...
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203 views

why is this query taking so long?

+----+-------------+-----------+----------+---------+------+----------+--------------------------------------------------------+ | Id | User | Host | db | Command | Time | State | ...
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1answer
2k views

Upgrading MySQL 5.1 to 5.5 on Centos 6 without removing dependencies

I'm trying to upgrade MySQL 5.1 to 5.5 using yum/rpm combo (yum to remove MySQL 5.1 and rpm to install MySQL 5.5). Most instructions I've found suggest to do first: yum remove mysql mysql-server ...
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845 views

Migrating from SQL Server to MySQL using MySQL Workbench tool

I'm trying to migrate few tables from SQL Server to MySQL using MySQL Workbench migration wizard. All work fine for structure migrations but when I go to the data migration section it throws an error ...