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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27 views

Why do these two queries (which I think are equivalent) rely on different keys?

We have a query that we don't like, since it ends up doing a full table scan. EXPLAIN SELECT count(*) AS c, location.name FROM study LEFT JOIN location ON study.location_id = location.id ...
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1answer
135 views

MySQL Join, Force NULL Row

I'm having a bit of trouble figuring out how to do this -- I need to select all rows from table t1, join table t2 -- but include a null row from t2 for each record in t1 (even if rows match in t2). ...
3
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1answer
6k views

How to append value of column with double quotes (add quotes around string)

I have a table with a column that is TEXT type. In the column are numeric characters. What I'm trying to achieve is to wrap those characters in double quotes. EXAMPLE: NAME ID QTY Apples ...
1
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3answers
1k views

How to auto replicate specific columns only from a table in MySQL

I want to make one master DB which replicates specific user data into other databases such as: username pass (hashed) email pin (hashed) timezone (int) They are all in one table and running on ...
0
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1answer
833 views

MySQL 5.1 -> 5.6 problem, select distinct order by limit query stops using index

I'm testing a MySQL 5.1 -> 5.6 upgrade, and I've run into an issue. I have a query that hits a ~30 million row table, selecting distinct IDs with an order by/limit restriction. Sample query is below:...
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4answers
855 views

Mass data upload from Excel - technology

I am a Developer seeking help in terms of DB technology for a specific requirement. I have done some research but can not conclude with list. Requirement: There will be a web application which will ...
0
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1answer
144 views

creating a 24 hours data table - Suggestions/improvements

I am planing to have a table to store the data based on every hour , in short I have a file with 24 hour data and I need to use this to populate a hourly bar/line graph. Below is a sample 24hr data ...
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2answers
2k views

MySQL ON DUPLICATE KEY UPDATE performance issue

We have a table with over 200k rows. Every row belongs to a category, there are almost 50k rows per category. What is the best way to update all rows of that category? We are using a script like ...
2
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2answers
570 views

Select different time

I looked on the internet and I found your post on the stackexchange. I will try to explain in more detail what we really need I do not know well to write English It is a system for airporttaxi id ...
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1answer
35 views

select where index + other field

Learning indexing I have made an index, consisting of usergroupid and birthdate I understand that queries will then benefit from indexing when searching usergroupid and/or birthdate But what ...
0
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0answers
176 views

Combine two mySQL sum queries into one which use different where clauses

I have two sum quires referencing different tables in mySQL. How can I combine the two in order to calculate the difference between the two values for each user in the database? Query 1: SELECT ...
1
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1answer
47 views

Multi Replications Plan on 2 servers

I need some advice about our new database deployment plan. We have 6GB of total mysql data(all innoDB) and innoDB_buffer_pool is set to be 16GB Ans we have 2 database servers.(plus 1 server for the ...
0
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1answer
176 views

Splitting Columns

I want to ask a complicated question and I think its advanced a little. I have a table has this design, its an attendance system. I need to split the time if the attendance count per day was not 2: ...
0
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0answers
4k views

Nesting multiple INNER JOIN within LEFT OUTER JOIN in sql on deifferent side of keyword

I am having some problems with one of the question's answered in the book "SQL FOR MERE MORTALS". Here is the problem statement Problem Statement Here is the Database Structure The Database ...
0
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1answer
84 views

Does having a big table that I do not query cause the whole DB to be slower?

I have a log table that I use for logging files sent to clients. I'm not querying that table, just use it for logging (INSERT) and when I need to check when something was sent to clients, usually once ...
3
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1answer
1k views

pt-table-checksum and row-based replication

The set up I work with is MySQL 5.5 in a master-slave replication configuration, but we have to use "MIXED" replication (statement and row-based) because we use an application that requires it, and it ...
0
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1answer
63 views

Is this statement syntactically correct? [closed]

$q = "SELECT var1, var2, var3 FROM tablename WHERE var_a = '$var_a' AND var_b = '$var_b' AND ( ( var1 = '$var1' AND var2 = '$var2' ) OR ( var1 = '$var2' AND var2 = '$var1' ) )"; This ...
1
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1answer
98 views

for what My mysql server get mr than 2 gig RAM on my vps?

imnot know english very well so sory for my bad dictation on my vps that has 4 gigabyte RAM and 4 core CPU and 220 gig HDD . i haved installed centos basic server 6.5 x64 and virtualmin last version ...
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0answers
313 views

How to change the domain name or IP address in mysql database in every tables

I was using Openfire chat server in Ubuntu, whose IP address was 192.168.1.15. Then, I wanted to move it to other ip (192.168.1.55), so i took a backup of my database. The database I was using is ...
0
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1answer
502 views

How to retrieve stored procedures from raw data

I have all the raw data from a database that I can't access through the mysql program anymore. I was able to get the tables by copying the .frm files over to the new installation of mysql, but I don't ...
3
votes
4answers
507 views

Best practice for a Table with private columns

I have a table with user data, where most of the columns can be public or private (so it will be shown or not on the app) and every user can decide which fields to hide. So far I had a couple of ideas....
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0answers
1k views

Moving datadir OK start, but socket error for mysql client

I'm trying to move my MySQL datadir from /var/lib/mysql over to /home/mysql (an ssd drive as I'm having iowait issues on /var/lib/mysql when MySQL is running on that drive). The OS is CentOS 5.6 (...
3
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3answers
3k views

MySQL Explain has different row count than slow query log

I have this entry in slow query log: # User@Host: user[host] @ [ip] # Thread_id: 1514428 Schema: db Last_errno: 0 Killed: 0 # Query_time: 2.795454 Lock_time: 0.000116 Rows_sent: 15 ...
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3answers
2k views

MySQL buffer pool usage + high load

We've got a quite powerful server: HP ProLiant DL360p Gen8, 2xIntel Xeon E5-2630 2.30GHz, 128GB of RAM. The whole data set should fit in memory: mysql> SELECT FLOOR(SUM(DATA_LENGTH+INDEX_LENGTH)/...
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0answers
425 views

Result of query not showing in phpmyadmin

I have a 500,000 row database that I am running a reasonably complex query on: SELECT yfog, (SELECT AVG(yds) FROM pbp_yards_gained p2 WHERE p2.yfog=p1.yfog AND type = '...
2
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2answers
2k views

Optimizing large MySQL SELECT WHERE IN clauses

How can the following SELECT WHERE IN case be optimized? I have a table with over 100 million rows with only 3 columns. The primary key (col1) is a 127 varchar. I am performing a SELECT col1 WHERE ...
0
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3answers
114 views

Select rows where 2 cells not the same

I have the following table: +----+-------+---------+---------------+ | id | owner | variant | EAN | +----+-------+---------+---------------+ | 1 | 101 | black | 1111111111111 | +----+--...
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0answers
27 views

What is safe way to restore mysql database?

When database is online. I want to restore dump file to it. Here is my plan: set global read_only=ON use root with super_priv to drop all databases do restore all databases set global read_only=OFF ...
2
votes
1answer
231 views

MySQL Replication - Master Master - Single Master write

I am looking to improve our fault tolerance for our persistent store. After reading several online docs about how to set-up master <> master replication, I'd still like to ask the experts about the ...
0
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0answers
20 views

How does database connection actually works? [duplicate]

I am wondering, on a practical level : what is a database connection? What does it represent for PHP/Java/Ruby/etc to have an opened connection for instance? What about the MySQL deamon? Does it ...
0
votes
1answer
50 views

How to sum the buy order and sell order in one row per each ticker

I have a table containing some trading information of several tickers and I would like to divide the data into sum(Amount) for buy and sell separately, grouping by each ticker. I have one table ...
3
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2answers
63 views

Why is MySQL ignoring my indexes?

I have a query select distinct id from patient where company_id in (1) and (name_last like 'peter%' or name_first like 'peter%' or remote_id like 'peter%') running on a table that looks like this ...
3
votes
2answers
316 views

mysql - is it possible to create a partition expression based on two keys / indexes?

if i have a table with, lets say 500 million rows, and among others there are two main individual indexes on that table. the table looks like: CREATE TABLE `t1` ( id_1 bigint unsigned not null, ...
0
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0answers
141 views

MySQL replication: Understanding content of binlog

I am using MySQL replication with GTID. I did mysqlbinlog to see some binary log. This is a section in binary log that I am considering: SET @@SESSION.GTID_NEXT= 'servre-uuid:248283'/*!*/; SET ...
3
votes
1answer
490 views

MariaDB ALTER TABLE produced a separate .ibd file, how can I re-integrate the data into the shared table space?

We have a multi-GB InnoDB MariaDB (recently switched from MySQL). For some reason, the value of innodb_file_per_table changed to ON (we wanted only one innodb data file explicitely). So when I ran an ...
0
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1answer
39 views

How can I get the user not to be listed twice?

I'm using the following query to list best times in a race. This works perfectly well but someone does the best record twice (for example, they finished the race in 15 seconds twice) they being listed ...
5
votes
1answer
10k views

Subqueries run very fast individually, but when joined are very slow

ypercube solved the problem. Subqueries were totally unnecessary, and the whole thing works with plain joins. It is still strange that MySQL's optimizer could not make use of my original query, though....
1
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1answer
1k views

Connecting to MYSQL on an EC2 instance

I'm trying to use Zapier to connect to our MySQL database in order to add results from forms (hosting with WordPress) directly into our internal database. The database is working properly and so are ...
1
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1answer
12k views

Images, PDF, audio and video files in MySQL

I am designing a database for an eCommerce website. How can I store images, audio, video and PDF files which are uploaded from the online users, in a MySQL database? I am using the InnoDB storage ...
1
vote
1answer
1k views

MySQL 5.6.17 running out of memory when opening table with many partitions

We are currently setting up a MySQL database (version 5.6.17) on an Amazon db.m1.large RDS instance for storing time series data. Each time series property of an object is stored in a separate InnoDB ...
0
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0answers
271 views

MySQL select query runs forever in Toad

I'm trying to run a simple SELECT query in Toad (for MySQL 7.2.0.2922). SELECT * FROM sometable When I click execute (or press F9) a small timer shows up in the status bar (bottom right) and it ...
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0answers
20 views

Can I include extra columns in a m->m mapping table? [duplicate]

I guess this is sort of an odd question, but consider this scenario. table classes (id_pk) table students (id_pk) table students_classes_map (students_id_fk_pk, classes_id_fk_pk, finalExamScore ...
0
votes
2answers
335 views

Converting MySQL 5.6.10 - 32 bit to 64 bit version

I am currently using MySQL DB Version 5.6.10 for 32 bit running in 64 bit Window OS.I want to change it to 64 bit without taking any dump..Can anyone help in this?
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2answers
505 views

how to design a database's table to store mysql spatial data in a parent child relation?

I want to store locations and polygon data in a parent-child relationship. I am using spatial data in MySQL and Google maps for polygon. Examples: 1. World 1.1 US 1.2 China 1.3 Japan 1.4 South ...
0
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0answers
47 views

Conditional value lists in MySQL

apologies in advance if the language I use here is insufficiently specific. Please let me know if there's anything that I can clarify. Does MySQL provide a means of creating conditional value lists a ...
1
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1answer
100 views

MySQL: Find ID with only 2 attached IDs in subtable

I've got 2 tables. 1 containing my Threads and 1 containing the users attached to these threads. I want to find the ThreadID with 2 specific UserIDs attached, no more no less. This is what I've come ...
0
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2answers
228 views

Alter auto-increment of table with 16 million rows

Learned this the hard way. Need to alter a table's auto-increment with 16 million rows. Now, it's taking quite sometime. Any estimate how long it would take? Sorry.
0
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1answer
74 views

mysql hardware refresh + version upgrade

currently I am running MySQL 5.0.80 on windows server 2003 (x64), 64gb memory, I have a master and 2 slaves. It's a large 400 gb Database. I am setting up all new hardware (SAN + dedicated MySQL ...
0
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1answer
40 views

Does column size increase break SELECT *?

I searched a little bit on this topic before realizing it is somewhat tricky (for me, at least) to come up with an effective search phrase for it because it overlaps with other common topics. So here ...
2
votes
1answer
132 views

Wordpress blog where pages are almost-always served from cache: SSD or more RAM?

I am working on the design of a Wordpress blog which when finished will almost-always serve pages from disk cache and this is because all posts will be published in batch and then cached, with at ...