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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Two different MYSQl instances on same machine?

I have MySQL 5.6 installed (Linux). /var/lib/mysql /etc/my.cnf I have a cold backup that I am recovering: /var/lib/mysql_backup /etc/mybackup.cnf In April I was able to get the backup started ...
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1answer
1k views

Intermittent connection errors

I am experiencing occasional connection errors from my webserver to one of my databases. The code attempts to connect. If it fails, it sleeps for 1 second, then retries, then (if it still fails) ...
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2answers
108 views

Anyway to optimize complex view?

In the system, Files can belong to either products, clearances, business_lines or titles. Clearances are records that represent a combination of a title and a product. Products are collections of ...
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1answer
43 views

Should I drop this column or is there a query that can achieve a results table without duplicate columns?

I use a column named active in several of my database tables to adjust whether a particular entry/row/user/etc should be included in future query result tables instead of deleting the information. ...
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2answers
11k views

query_cache_type = 0 vs query_cache_type = 1

Recently, I moved from standard MySQL to Percona, and used the Percona Wizard to generate my.cnf. However, I can see that, by default, the generated settings for my.cnf use query_cache_type = 0. (...
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1answer
9k views

Row size error with MySQL

I'm running a MySQL server on my Macbook (for testing). Version is 5.6.20 from Homebrew. I started running into "Row size too large" errors, and I've been able to reduce it down to this test case. ...
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1answer
208 views

Adding time to an event that runs on a weekly basis

I have this event that runs every Thursday CREATE EVENT le_drop_database ON SCHEDULE EVERY 1 WEEK STARTS CURRENT_DATE + INTERVAL 3 - WEEKDAY(CURRENT_DATE) DAY DO BEGIN drop database carbon; ...
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1answer
86 views

Is data warehouse monitoring same as database monitoring? [closed]

I have a requirement, where data warehouse population is to be monitored. I am in confusion, and needed a clear picture. Is data warehouse different than database? eg. For monitoring database we ...
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1answer
2k views

Import multiple CSV fields into one MySQL field

I'm trying to import our CSV data log into our MySQL. The first two fields of the CSV are Date and Time, and I would like to combine that into one date time (which can be searched) onto MySQL. CSV: ...
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107 views

Slow mysql UPDATE with IF() conditions

not sure why I can't even EXPLAIN this query. Mysql refuses to EXPLAIN it. Table contains a million meaningless test entries. Full schema and data dump of the table available here: http://runboard....
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0answers
121 views

Mysql syntax error when i add on completion preserve

I have written this event in mysql DELIMITER $$ CREATE EVENT le_drop_database ON SCHEDULE EVERY 1 WEEK ON COMPLETION PRESERVE STARTS CURRENT_DATE + INTERVAL 4 - WEEKDAY(...
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1answer
145 views

Translating MySQL query to PostgreSQL

I have a query which works fine in MySQL, however when I try to recreate the same query in PostgreSQL (same DB structure) I just get a syntax error. MySQL: SELECT ticket.queue_id, queue.name, ...
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1answer
231 views

Is normalization advisable on transactional data?

I have read a lot of articles about normalized vs denormalized schemas, but I find very little mention of the cost of row insertion. I am considering the impact of converting a 100% denormalized ...
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1answer
196 views

queries for hierarchical data

This table is a questions and answers CMS and i want to know how data is fetched from these tables. +------+----------+-------+ | id | parentid | type | +------+----------+-------+ | 1 | 0 ...
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0answers
21 views

RAID configuration for mysql [closed]

I attached 4 10G disks to mysql Server and I used RAID 0 but still same mysql performance the same, Do I have to change configuration in my.cnf to let mysql know about RAID 0
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0answers
130 views

What is the difference between Row and Table Expressions in MySQL

Can anybody explain with example what is a Row and Table expression and what is the difference between them. Any example for clarification will be appreciated.
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0answers
81 views

Many small queries or one single query

This is not exactly a question, more of a survey. Here at BlackBean we have a time series aggregation and analysis platform built on top of MySQL, where each client have your own database, and each ...
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1answer
27 views

Determining which database instance makes biggest IO

Assuming that I have a dedicated server on which I am running multiple instances of mysql and postresql servers. How without iotop determine which instance in particular time (proc/pid/io shows data ...
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1answer
1k views

Table is dropped but ibd file still exists

I was dropping some unwanted tables I have in the MySQL. When I run a drop table, its showing table doesnot exists. But when a check in the data directory, the .ibd file exists and its almost 1GB. How ...
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1answer
3k views

MySQL RDS Instance eating up memory and swapping

I have an issue with memory on a RDS instance which is of db.m2.4xlarge class. Below are the specifications of the RDS instance Instance Class: db.m2.4xlarge ( 68.4 GB of RAM ) Engine: ...
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2answers
642 views

RAID configuration for mysql

I attached 4 10G disks to mysql Server and I used RAID 0 but still same mysql performance the same, Do I have to change configuration in my.cnf to let mysql know about RAID 0. this is my mount ...
1
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2answers
315 views

Getting a Deadlock,

I have this code : public void saveItems(List<Pair<Item, MapleInventoryType>> items, int id) throws SQLException { PreparedStatement ps = null; PreparedStatement pse = null; ...
0
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1answer
579 views

MySQL JDBC does not behaves as the MySQL Workbench

I'm running the following from the MySQL Workbench, and from my local tomcat using jdbc. START TRANSACTION; CREATE SCHEMA IF NOT EXISTS `ROOT`; CREATE TABLE IF NOT EXISTS `ROOT`.`all_tables` ( `...
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0answers
68 views

Mysql database recovery in linux

Is there anyway to get back database if I deleted database. Is mysql creates temp file which contain temporary data from database and whether I can recover from that Edited: cp my.cnf my.cnf41 mv /...
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1answer
1k views

MySQL max_connection value

Questions I got a 12 GB machine with apache & myqsl, i have may apache max_client set to 150 will this cause some bottlenecks with the 50 max_connection in mysql? What value should I set mysql ...
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2answers
219 views

Rank variable value in MySQL is always being set to null

In a sample procedure I am trying to find the rank the of the cities according to the number of offices. I have a Location Table and an Office Table and a location can have multiple offices (...
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1answer
154 views

Indexing the difference between two columns in MySQL

Is there a way to optimize/index a query that sorts the difference between two columns. I have a modest sized table of 5 million rows that I'm trying to do the following: SELECT pk_column, column_x, ...
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0answers
176 views

Storing DB credentials in an application source code?

I am making an app which connects to a DB, and the app will have plenty different userslogins. Is it a good design choice to have a specific DB login/password for the application, using which the ...
0
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1answer
419 views

SymmetricDS not using Lookup Transform on primary key

I'm syncing records between two MySQL databases using SymmetricDS, but need to keep the primary key (fieldname = "id") fields unique. Symmetric doesn't seem to want to obey the "lookup" transform_type ...
1
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1answer
791 views

InnoDB deadlock with INSERT .. SELECT

I am trying to understand why a deadlock occurs when two workers in parallel are running INSERT .. SELECT queries on a table which has both 1) auto incremented primary key, 2) a unique index on ...
0
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1answer
43 views

I cant figure out the error probably with the date field in this mysql stored procedure

This is my empDetails table I am trying to create a stored procedure on. mysql> describe empDetails; +---------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | ...
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13 views

SQL Select a rolling count of total transactions over time [duplicate]

I need to get a set of total transactions over time on a weekly interval. Essentially I need a total-transactions-to-date column. When I group by WEEK(Date) I get the amount of transactions for that ...
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0answers
61 views

Change a query so it no longer takes 20 mins and uses a 93G tmp table

Edit: So how would I go about changing this query to something more sane (given that I can work around the hibernate madness) This might be a whole different problem, but Hiberate has created a ...
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1answer
82 views

Proposal: MySQL blob handling revision [closed]

Why does MySQL store blobs in the direct table rather than off to the side so that if it needs to read the corresponding stuff it will read the stuff off to the side? Essentially it would create its ...
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1answer
4k views

In place upgrade from MySQL 5.5 to 5.6.11 removes all users from user table

On Windows, I upgraded from 5.1 to 5.5 no problem. Copied my 5.1 data folder into my 5.5 instance Started mysqld skipping grants Ran mysql_upgrade All good, but going from 5.5 to 5.6: Copied ...
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0answers
83 views

Double subquery is very slow, but independently they are fine

I have this query: SELECT mac, pid, node_category.name, status, computername, user_agent, detect_date, regdate, unregdate, last_dhcp, node.notes, (SELECT ip FROM iplog WHERE iplog.mac = node.mac ...
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1answer
30 views

MySQL - reformat a column value dependant on existing value

Am needing to provide a concatenated field from a select query which is dependant on existing values. SELECT `delegate`.`FirstName` AS `First Name`, `delegate`.`LastName` AS `Last Name`, `...
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1answer
3k views

Multi-Column Full Text Search Going Very Slow

I have a full text index on a table articles for the columns content, title and keywords When doing the search on each of the columns, like so select count(1) from articles where match(content,title,...
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83 views

MySQL master/slave replication - replicate all tables

I am doing a master/slave replication, but getting errors about my tables does not exist. Is there not a way where i can make the whole table structure replicate aswell? Thought it did on default tbh.
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1answer
33 views

Useful guide & FAQ for Application+SQL [closed]

Of course when you are making your first application for fun it doesn't matter that much how you deal with things. But when you need everything to be up to the current standards you don't always know ...
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0answers
276 views

Unresponsive MySQL database

I've setup a MySQL server on Ubuntu machine. When running a heavy query (the table has over 1M rows), the database becomes unresponsive. Upon connection it returns: Can't connect to MySQL server ...
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2answers
334 views

“All joins can be rewritten to sub queries”, is this statement true?

I wonder if there any case that a join can not be converted to a sub-query. BTW: I am not discussing advantages and disadvantage of using sub-query or using join.
2
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1answer
314 views

Innodb DB Consuming IO even when no operations are being done

I am currently doing some stress testing where I am pushing inserts to the database as fast as I can. The simulation inserts 10000 records per second. After inserting around 200 million records I ...
0
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1answer
74 views

Can a primary key of one table be a foreign key of another table?

I am working on a scenario like this : I have an employee table which has columns like this Employee_ID First_Name Last_Name Employee_Designation Also I have a Joining_Vital table Employee_ID ...
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2answers
522 views

ON DUPLICATE KEY UPDATE faster than UPDATE

I have a table with about 17 million rows: mysql> describe humans_we_respect; +---------------------+-------------------------------------------------------------------------+------+-----+---------...
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1answer
112 views

How to change rows to columns in mysql?

I have data as following(it is just an sample, I have 100+ different types.): advertiser_id activity_type counts 1 1 2 1 2 5 2 1 ...
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2answers
1k views

0xDBE how to connect over local socket?

I want to connect to mysql over socket. This is what I'm trying to do: and it's not working. This is how it works in mysql workbench:
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1answer
87 views

mysqldump - select table in database only if it contains a specific string

(I'm new to Database Administrators, and am not a Database Administrator. However I originally asked this question on Stack Overflow (here) but didn't get any answers. Sorry if this is not the right ...
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1answer
983 views

Can't restore from mysql dump file

I used mysqldump command to export/dump .sql file with rows like: String cmd1 = mysqldump + " -h" + host + " -u" + username + " -p" + password + " " + "--compact --no-create-info " + "--where=ID=" + "...
4
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2answers
116 views

How to search with partitions in my query?

Table structure: mysql> show create table transaction_event_items\G *************************** 1. row *************************** Table: transaction_event_items Create Table: CREATE TABLE `...