MySQL : Open-Source, Relational Database Management System

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How to do a case sensitive search in WHERE clause?

I want case sensitive search in SQL query. But by default, MySQL does not consider the case of the strings. Any idea on how to do a case sensitive search in SQL query?
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ALTER TABLE on a large table with an indexed column

I have a large table with a VARCHAR(20) column, and I need to modify that to become a VARCHAR(50) column. Typically, performing an ALTER TABLE (adding a TINYINT) on this particular table takes about ...
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How to stress test a SQL server?

I've been tasked to stress test our MSSQL Server and MySQL Server. I would like to know if there are any tools or scripts which I could use on our current systems and the new system to compare ...
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How to solve “The table … is full” with “innodb_file_per_table”?

I have a MySQL database that holds a large amount of data (100-200GB - a bunch of scientific measurements). The vast majority of the data is stored in one table Sample. Now I'm creating a slave ...
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Running SQL Query on all databases

I have one hosting account using cPanel and phpmyadmin. I have 50 databases under this account, all WordPress. I need this query modified so that it runs through all databases to update the ...
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How to Best Implement nearest neighbour search in mysql?

So, in short, What should be the data type of latitude and longitude? What SQL command I should call to get the first 100 nearest restaurants for example? Detail: I have 100k biz record each with ...
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MYSQL ERROR 2049 (HY000): Connection using old (pre-4.1.1) authentication protocol ref used (client option 'secure_auth' enabled)

when I tried to restore all database dump which is in 5.0 version to 5.6 version, it got restored and after that when I tried to reconnect, am getting the following error ERROR 2049 (HY000): ...
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PHP -> Mysql persistent connection pooling WITHOUT mysql_pconnect - Possible?

I have been trying to figure out a nice way of doing this for a while now. But have had a hard time finding the right pieces to do this. I am guessing this must be possible. To put it in simple terms ...
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What could be causing strange query timeouts between PHP and MySQL?

I am the senior developer on a Software-as-a-Service application used by many different customers. Our software runs on a cluster of Apache / PHP application servers, powered by a MySQL backend. On ...
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Deleting all duplicates

I am trying to delete all the duplicates but keeping single record only (shorter id). Following query deletes duplicates but take lot of iterations to delete all copies and keeping original ones. ...
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How can I optimize this MySQL query further?

I have a query that is taking a particularly long time to run (15+ seconds) and it is only getting worse with time as my dataset grows. I have optimized this in the past, and have added indices, ...
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Deleting large amounts (4 million rows) of mysql data efficiently, on a very regular basis

We have a mysql table that at any given time has about 12 million rows. We need to delete old data to keep the size of the table somewhat manageable. Right now we are running this query daily, at ...
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How to search a MySQL database with encrypted fields

Suppose I need to encrypt certain table-fields of a MySQL database. Additionally, I need to search some of those fields I did encrypt. How would one search those fields anyway? Decrypting each ...
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How to resolve too many connections and fatal error in mysql running on vps

I am running an application PHPlist on my linode server, simultaneously running 12 PHP scripts, each of which opens a MySQL connection. Now when I access PHPlist it often shows this error: Fatal ...
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Why would an UPDATE SET REPLACE() statement match rows, but change none and give no warnings?

I'm seeking a certain string in a field and want to replace it with a new string. Specifically, I want all references to one URL to be changed to another URL. I've crafted this SQL statement and am ...
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Dynamic SQL in MySQL stored routines

According to the restrictions on stored routines and triggers, dynamic sql cannot be used (restriction lifted for stored procedures in version 5.0.13 and later). Why is this limitation in place? And ...
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Why would MySQL do serial synchronous I/O?

When looking at a particularly annoying query over MyISAM tables which takes a long time to execute on a number of occasions, I have noted that MySQL seems to expose a rather strange I/O pattern: when ...
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Slow MySQL Database Import with mysqldump and USE .. SOURCE

I have about 12 tables in MySQL innoDB, one of them has 11 million records in it. I used this command to back things up: mysqldump -u [USERNAME] -p [DBNAME] | gzip > [/path_to_file/DBNAME].sql.gz ...
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Trigger to UPDATE after UPDATE?

I want to make a trigger to record the time of any update as CREATE TRIGGER col_update AFTER UPDATE ON col FOR EACH ROW BEGIN UPDATE col SET updated=NOW() WHERE id=NEW.id; // or OLD.id END The ...
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MySQL reads / writes per table

I am optimising our DB. Essentially I am trying to find the most written and the most read tables in our db. After that I will follow by sym-linking those tables into separate drives. Is there a way ...
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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 ...
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Error creating foreign key from MySQL Workbench

I'm trying to synchronize schema changes from MySQL Workbench to my database. I'm getting the following error when it tries to create a foreign key: Executing SQL script in server ERROR: Error 1005: ...
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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 ...
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MySQL Workbench Database Sizes

I'm trying to find the total size on the hard disk that all of my MySQL Workbench databases are using. Does anyone know of an easy way to figure this out? If nothing else, the default location ...
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How to cast an integer to a boolean in a MySQL SELECT clause?

I'm new here so be kind to me. I have the following scenario: I have many tables which, for the sake of simplicity, are represented in a View in my MySQL database. My problem is that I need a value ...
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What are the trade offs for incrementing ids vs. fulltext keys for foreign key designs?

In a lot of relational database designs there are fields that are referenced in other tables. For example consider a user table with a unique username and a second table storing address data. One ...
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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 ...
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Optimization problem: compound clustered keys, flag conditions and index-merge

Three tables: product: with columns: ( a, g, ...a_lot_more... ) a: PK, clustered g: bit-column main: with columns: ( c, f, a, b, ...a_lot_more... ) c: PK, clustered f: bit-column (a, b): UQ ...
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Can I have one table be an “alias”, or “symlink”, to another?

I have two tables with the same structure, A and B. A certain application is written so that it always writes the same data to both tables. After a discussion with a colleague about the potential to ...
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BigInt or Varchar for a large number I won't ever sort / calculate on

I need to store users' Facebook IDs in a column in my DB. The ID always consists of only digits, and can be as large as a number in excess of 500 million. Considering that I won't ever need to do ...
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Is it possible to change ENUM() lists?

I wasn't sure if changing ENUM() list isn't possible so I made a test. In MySQL v5.1.58 I made a test InnoDB table that contains one field called 'bool' of type ENUM('yes', 'no'). Then I executed... ...
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How can I improve my SQL statement with weekly results with week starting on Thursday or any other day of the week?

I am a total newb, and I couldn't find a good way to do this anywhere. I have a database table that contains statistics that are recorded at various time throughout the week. The reporting week ...
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Generating Invoices and Tracking

Every 2 weeks, the system will generate the invoices for the companies. Company will receive an invoice on the 1st and 16th every month. (It will run via Cron Job every 2 week. It scan through the ...
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What is the usage of performance_schema in MySQL 5.5?

I have upgraded to MySQL version 5.5. There, I had observed performance_schema in the schema list. What is the usage of this new schema..? How can we monitor using this schema..? What are the ...
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MySQL 5.1 InnoDB Configuration / 24GB RAM - bi-xeon high load

i'm running a facebook app which currently has 300 - 600 concurrent users (and growing). To get the hardware ready for growing i changed my i7 / 12gb ram / 2x 80gb intel x25 ssd's (debian 5.0 / mysql ...
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Does making a field unique make it indexed?

If I make a unique constraint on a field, do I also need to make an index on that field in order to get a scalable insert time? Or is this done for me (even if the index it uses isn't publicly ...
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MySQL LDAP authentication

Is LDAP authentication and authorization in MySQL possible? What are the requirements (MySQL version, third-party software etc.)? How it's organized? Thanks.
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Friends relations in MySQL

I'm developing a friendship relation in MySQL where friend relation is mutual. If A is friend of B, then B is friend of A. If one of the users end friendship then relation drops. I want to learn which ...
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Performance of a Trigger vs Stored Procedure in MySQL

A post here on DBA.StackExchange (What are the best practices for triggers to maintain a revision number on records?) has spawned an interesting question (at least, interesting to me) regarding ...
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SELECTing multiple columns through a subquery

I am trying to SELECT 2 columns from the subquery in the following query, but unable to do so. Tried creating alias table, but still couldn't get them. SELECT DISTINCT petid, userid, (SELECT ...
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MySQL Partitioning: Is there a performance tradeoff between number of partitions and size of each partition?

I have a large table (several 100 million rows) that I would like to efficiently partition. My question is whether there is a tradeoff between partition size and number of partitions. As far as I ...
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Transactional DDL workflow for MySQL

I was a little surprised to discover that DDL statements (alter table, create index etc) implicitly commit the current transaction in MySQL. Coming from MS SQL Server, the ability to do database ...
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How to update one table based on another table's values on the fly?

I have a table in the name of ips as below: CREATE TABLE `ips` ( `id` int(10) unsigned NOT NULL DEFAULT '0', `begin_ip_num` int(11) unsigned DEFAULT NULL, `end_ip_num` int(11) unsigned DEFAULT ...
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How to create a database for unknown kinds of data?

I am in the process of designing a database for a new PHP/MySql-based application. My problem is that I do not and cannot represent what should be saved in the database because it is unlimited and ...
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MySQL : DROP TABLE Starting with a Prefix

EXAMPLE : I have more than 30 tables starting with a prefix "dp_" and about 12 starting with "ex_". QUESTION : How can I drop all tables starting "dp_" in one query ?
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How do I find out if a procedure or function exists in a mysql database?

How do I find out if a procedure or function exists in a mysql database? and is there any discovery option? like a show procedures; (e.g. like show tables;)
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Data Compression Through Base36 Encoding

I'm trying to store a lot of large numbers that truncate when stored as INT values. Unfortunately they are too large for this type. I'm thinking about using Base36 encoding to accomplish this. Are ...
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Differences between “Unique Key” and “Primary Key”

What are the major differences between Unique Key and Primary Key in MySQL?
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How costly is opening and closing of a DB connection?

How CPU intensive is opening and closing of a DB connection (for a web app) in MySQL ... when the DB software is on localhost? ... when the DB software is on another machine?
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Call a stored procedure from a trigger

I have created a stored procedure in mysql using the following syntax. DROP PROCEDURE IF EXISTS `sp-set_comment_count`; DELIMITER $$ CREATE PROCEDURE `sp_set-comment_count` (IN _id INT) BEGIN -- ...