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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1answer
130 views

CASE conditions in SELECT statement [closed]

I have the following SELECT statement: SELECT expt_id, iso_stain, test_stain, stain_type CASE WHEN stain_type = 'Blue' THEN iso_stain = 'NA' CASE WHEN statin_type = 'Hematoxylin' THEN ...
0
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1answer
132 views

Set MySQL option to restore MySQL server after deleting ibdata1

ON an Ubuntu Server 12.10 machine, I had attempted to delete the ibdata1 file before reading Rolando's explanation about how exactly to do so. Specifically, I had not set innodb_fast_shutdown = 0 ...
1
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1answer
89 views

How Much Resources Does the BLACKHOLE Storage Engine Consume?

I'm going to add a MySQL Relay Slave which use BLACKHOLE Storage Engine. The relay slave will just filter some databases binlog to downstream slave. Our MySQL Master generates about 15G a day in ...
5
votes
1answer
734 views

Is it Possible to Recover Data from a BLACKHOLE table? [closed]

I had created table with engine BLACKHOLE basically the BLACKHOLE storage engine acts as a “black hole” that accepts data but throws it away and does not store it. Retrievals always return an empty ...
7
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2answers
14k views

MySQL performance problem using indexed datetime column

I tried to solve the following problem for about one hour now and still didn't get any further with it. Okay, I have a table (MyISAM): +---------+-------------+------+-----+-------------------+-----...
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0answers
333 views

One table for article comments, video comments and photo comments or multiple tables?

First DBA question. Greetings people. I hope I'm not duplicating a question but it's very hard finding database design related questions here (for multiple comment tables), as all 'design' questions ...
0
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0answers
233 views

Load data from file only for specific column based on other column value

I am familiar with basic usage of 'load data local infile' and importing specific columns only. What I want is however to import a single column from file based/related on data from another column. So ...
0
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1answer
57 views

Query a database for empty tables

In my system there are two tables called ‘faculty’ and ‘faculty_assets’. I need to delete faculty by faculty from the ‘faculty’ table. But system should allow deleting the faculty when only ...
1
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1answer
72 views

Count/Statistic for number of SHOW INDEX queries in MySQL/MariaDB 5.5 [closed]

We have a lot of SHOW INDEX FROM queries coming from our ORM layer. Usually there is a mechanism to prevent this but it doesn't seem to work at the moment. To better analyze the problem it would be ...
1
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1answer
814 views

Cartesian product of two tables not working as expected in MySQL but fine with SQlitee?

I was practising some sql joins and decided to create a schema online rather than using my local database on sql fiddle. My schema is pretty simple table 1 (5 entries): (emp->{id,name,dep}) table ...
2
votes
1answer
301 views

Is there a difference between RANGE and LIST method for partitioning by consecutive integer values?

I have a table with a year column that has consecutive values -- 2000, 2001, and so on. It's a read-heavy MyISAM table, with 25+ million rows for every value of year and a comparable set inserted in ...
1
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1answer
75 views

How to put this particular constraint on this link table in MySQL? [duplicate]

I have the following three tables in MySQL: Store, Groups, StoreGroup. A store can belong to several groups. StoreGroup is the link table that records the groups a store belongs to. The Groups table ...
2
votes
1answer
2k views

MySQL consistent nonlocking reads vs. INSERT … SELECT

So, from my reading of the MySQL 5.5 documentation and some experiments I did with colleagues, I understand that the following is the case: With InnoDB tables, a simple SELECT statement (one that ...
3
votes
2answers
1k views

MySQL memory usage issues?

I have a MySQL instance running on my Ubuntu server that is eating up most of the memory on the machine. I currently have 2 GB of ram installed on the machine, and MySQL is using 1983 MB. Most of my ...
1
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1answer
209 views

MySQL Replication Lag Almost 23 Hours

I came into a new environment where the production DB was running on MySQL 4. Replication is usually about an hour behind but in the last few days it has been well over 24 hours behind. I'm not ...
0
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0answers
314 views

Finding the right MariaDB configuration

I’ve read several articles about how to configure MySQL/MariaDB, but now I’m kind of confused how to find the right values. Some articles suggest not choosing to high values, others recommend adapting ...
0
votes
1answer
86 views

MySQL grant privileges has no effect

I've executed the following queries: GRANT USAGE ON my_db.* TO my_user@127.0.0.1 IDENTIFIED BY 'pass'; GRANT ALL ON my_db.* TO my_user@127.0.0.1; GRANT SELECT, INSERT, UPDATE, DELETE ON my_db.* TO ...
-2
votes
1answer
55 views

using ubuntu 14.04 when i use this command getting the error

just installed mysql server using sudo apt-get install mysql server when i try to display the database in terminal getting this type of error SHOW DATABASE; ERROR 1064 (42000): You have an error in ...
0
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1answer
97 views

Repair table field: Import/append records from specific backup field if they are not null

One of my 3rd party applications that writes to my production MySQL database mydb has nulled SOME of the data in one of my fields myfield in table mytable. I'm trying to import only the NON null ...
0
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1answer
2k views

group by clause without aggregate function

I've always assumed GROUP BY was designed specifically for aggregate functions and in all other circumstances you should use ORDER BY. For example, we have three tables: orders, shippers, and ...
2
votes
1answer
716 views

Why/when does creating a mysql trigger require SUPER privileges?

I'm attempting to parse and understand what the MySQL doc says about when SUPER privileges are required for creating triggers. They say: If binary logging is enabled, CREATE TRIGGER might require ...
1
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2answers
453 views

Creating a database with only MySQL command line?

The linux server on which I'm attempting to create a MySQL database has many difficult to work with permissions. My supervisor has tried to install MySQL Workbench on the server, but has been unable ...
2
votes
3answers
479 views

Will MySQL be effective when selecting a row from a table with billions of records? [duplicate]

Note: this is a hypothetical scenario Lets say that: I'm running MySQL, InnoDB engine, UTF-8 encoding I have a table with 50+ billions of rows The tables primary key is a BIGINT The table also has ...
3
votes
2answers
1k views

UPDATE query with JOIN taking forever

I'm not very good with databases so please keep in mind even if the solution sounds like something everyone would have already tried, please post it because I likely have not tried it and it would ...
5
votes
1answer
14k views

mysql logging activity from specific user or ip

I have mysql server. The server is accessed by my application, and by external auditor (person using mysql workbench). The auditor has specific user and password and dedicated IP and it is granted ...
2
votes
1answer
65 views

Change column without interrupting service

We need to change the data type of a column in a large table (~1.7 GiB) from VARCHAR(1024) to VARCHAR(512) in order to be able to create a secondary index over two columns. We're using MySQL 5.6 with ...
2
votes
1answer
52 views

Is it possible to import a single mysql database directory?

I am somewhat new to mysql. I created some databases recently and, to back them up, I just copied the folders with those database names in the mysql data directory (i.e containing only db.opt, .frm, ...
0
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1answer
43 views

MySQL Insert with Select

Trying to insert data to a table with values from different tables. INSERT INTO class_teachers_section(class_ref, teachers_ref, section_ref) select (select class.id as class_ref from class ...
2
votes
2answers
412 views

Should I drop a foreign key if I use a soft delete?

"ON UPDATE" scenario never happens in my application. As soft delete is used, "ON DELETE" cascade and restrict scenario never happen as well now. Then, should I just drop foreign key because I have ...
3
votes
1answer
837 views

A question on MySQL SELECT Algorithm/Function

Let's say I have 100,000 rows in a table, and each of the rows has a boolean value. Only ten of these rows have a value of 1, the rest are 0. How would MySQL perform a SELECT on only the rows with a ...
0
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0answers
151 views

Mysql query with LIMIT much slower under RDS (5.6) than old 5.1 system

We inherited an old legacy system running on mysql 5.1, and moved it to RDS running 5.6. One query is running much slower - it can take up to 20 minutes to run, where previously it took only a few ...
2
votes
1answer
700 views

MySQL InnoDB table accepts Non-Existent Foreign Key

Using EasyPHP 14.1 VC11 and phpMyAdmin (4.1.4) to create a website project in my home computer. The MySQL version is 5.6.15 according to the EasyPHP administration page. Working on Windows 7 64-bit. ...
3
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1answer
8k views

Mysql INSERT INTO .. ON DUPLICATE KEY UPDATE

I'm trying to do the following query in mysql 5.5 INSERT INTO countingTable( image_count, article_id ) SELECT COUNT( article_id ) AS sum, article_id FROM imageTable ON DUPLICATE KEY UPDATE ...
1
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1answer
166 views

MySQL Workbench sync keeps requesting the same changes

I am using MySQL Workbench, and when I try to "synchronize" it with my remote database, it keeps detecting some changes to make. Specifically, the most recurrent ones are: Dropping foreign keys and ...
0
votes
2answers
1k views

Keep total transaction in invoice application

I want to make an application called as Invoice Application with MySQL database. Now I have designed this database. Now I want to know is this database good for Invoice Application. I will use MySQL ...
3
votes
2answers
163 views

Do MySQL optimizations hold for MariaDB also?

I am a developer who will be starting a new project soon in which database performance will be crucial. The current candidate for the backend is MariaDB. I have worked with MySQL and MariaDB before in ...
0
votes
1answer
121 views

MySQL: How to calculate potential wait time?

I'm trying understand the relationship between WAIT_MS and COUNT_STAR. Is this saying the average wait time is 3.2s and occurred 11,543 times for a total of approximately 10.5hrs of aggregate wait ...
0
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0answers
50 views

Restore data from MYSQL Bin log

I am trying to restore some data from mysql bin log file. But when it encounter some special characters, query gets break and I am not able to continue after that. Is there any way to handle special ...
4
votes
1answer
3k views

Loop through all users in MySQL and add REQUIRE SSL flag

How do I loop through all users (we have > 3000) in a MySQL database, and add the REQUIRE SSL flag to the every account? I don't want to modify the existing users permissions, host, or password, ...
2
votes
1answer
73 views

Understanding JOINs and why the syntax works the way it does

Heyo, I'm confused as to how this works: UPDATE original SET price=(SELECT price FROM new WHERE new.id=original.id) WHERE id IN (SELECT id FROM new); What it does is updating an original table ...
1
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1answer
407 views

How to loop SQL query in mysql?

I have a SQL query as following: SET @thedate := CURDATE(); create temporay table tmp1( ... where thedate=@thedate ); create temporay table tmp2( ... where thedate=@thedate ); delete from tbl1; ...
2
votes
2answers
2k views

Changing data type from mediumint to int without downtime

My current table is using MEDIUMINT for ID column ‘primary key auto increment’. The current table records soon will reach the maximum value for mediumint which is 8388607. That being the case, I need ...
-6
votes
1answer
234 views

How to run mssql server dependent application to mysql workbench [closed]

I am very new in mysql workbench. I have created an application in c# which uses sql server 2008 r2 database. Now i have migrated my database on mysql workbench. i want to run my application now. My ...
0
votes
1answer
691 views

MySQL asynchronous multi master replication conflict resolution

I have setup Multi Master replication, following this blog thread: http://0wned.it/geek-bits/guides/mysql-multi-master-replication/ And now it synchronizes perfectly, up until the moment the ...
2
votes
1answer
3k views

mysql privilege to kill processes of other users

I have a percona mysql database. The version is 5.5.29-29.4-log. I have created a user called admin which should be able to kill processes initiated by other users, i.e worker. GRANT SELECT, ...
0
votes
1answer
34 views

move content from one table to another table and add a new value

I need to move content from one table to another table, this part is done: INSERT INTO `insc_mwc` (`nome`,`empresa_idempresa`,`cat_mwc_idcat`,`points_pontos`,`n_registo`) SELECT nome,...
1
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1answer
109 views

How to update MySQL with CentOS 6 in most unintrusive way - in regard to perl and PHP packages? [closed]

For my few hobby projects (web games + forums) I have been using CentOS 5 (then 6) with Drupal and PostgreSQL plus few custom PHP and Perl scripts written by mysef. Since PostgreSQL version delivered ...
1
vote
1answer
303 views

MySQL: can a table get stuck in the table cache?

I've asked this question on the ServerFault stackexchange, someone directed me here. I'm a PHP developer and am responsible for a set of PHP scripts that run on a shared host running FreeBSD, that ...
2
votes
1answer
168 views

MYSQL Query - Unexpected result in text messaging database [closed]

On a text messaging database I have built, I am trying to return the total amount of messages a user has sent and the total number of messages a user has received. I have the following code: SELECT ...
1
vote
2answers
103 views

Merge output of two Queries MYSQL

I have a mysql table with the following schema: +------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +------------+-------------+---...