Database

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General

  • https://en.wikipedia.org/wiki/Database - an organized collection of data. The data are typically organized to model relevant aspects of reality in a way that supports processes requiring this information. For example, modeling the availability of rooms in hotels in a way that supports finding a hotel with vacancies.

Database management systems (DBMSs) are specially designed applications that interact with the user, other applications, and the database itself to capture and analyze data. A general-purpose database management system (DBMS) is a software system designed to allow the definition, creation, querying, update, and administration of databases. Well-known DBMSs include MySQL, PostgreSQL, SQLite, Microsoft SQL Server, Microsoft Access, Oracle, SAP, dBASE, FoxPro, IBM DB2, LibreOffice Base and FileMaker Pro. A database is not generally portable across different DBMS, but different DBMSs can inter-operate by using standards such as SQL and ODBC or JDBC to allow a single application to work with more than one database.


  • https://en.wikipedia.org/wiki/Query_language - an be classified according to whether they are database query languages or information retrieval query languages. The difference is that a database query language attempts to give factual answers to factual questions, while an information retrieval query language attempts to find documents containing information that is relevant to an area of inquiry.



  • https://en.wikipedia.org/wiki/Column_(database) - a set of data values of a particular simple type, one for each row of the table. The columns provide the structure according to which the rows are composed. When a column allows data values of a single type, it does not essentially mean it only has simple text values. In relational database terminology, column's equivalent is called attribute.
  • https://en.wikipedia.org/wiki/Row_(database) - also called a record or tuple — represents a single, implicitly structured data item in a table. In simple terms, a database table can be thought of as consisting of rows and columns or fields. Each row in a table represents a set of related data, and every row in the table has the same structure.
  • https://en.wikipedia.org/wiki/Field_(computer_science) - a record divided into fields. Relational databases arrange data as sets of database records, also called rows. Each record consists of several fields; the fields of all records form the columns. Examples of fields: name, gender, hair colour.


  • https://en.wikipedia.org/wiki/View_(SQL) - the result set of a stored query on the data, which the database users can query just as they would in a persistent database collection object. This pre-established query command is kept in the database dictionary. Unlike ordinary base tables in a relational database, a view does not form part of the physical schema: as a result set, it is a virtual table computed or collated dynamically from data in the database when access to that view is requested. Changes applied to the data in a relevant underlying table are reflected in the data shown in subsequent invocations of the view. In some NoSQL databases, views are the only way to query data.

Database practitioners can define views as read-only or updatable. If the database system can determine the reverse mapping from the view schema to the schema of the underlying base tables, then the view is updatable. INSERT, UPDATE, and DELETE operations can be performed on updatable views. Read-only views do not support such operations because the DBMS cannot map the changes to the underlying base tables. A view update is done by key preservation.


  • https://en.wikipedia.org/wiki/Materialized_view - a database object that contains the results of a query. For example, it may be a local copy of data located remotely, or may be a subset of the rows and/or columns of a table or join result, or may be a summary using an aggregate function.



  • https://en.wikipedia.org/wiki/Database_index - a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes are used to quickly locate data without having to search every row in a database table every time a database table is accessed. Indexes can be created using one or more columns of a database table, providing the basis for both rapid random lookups and efficient access of ordered records.








  • https://en.wikipedia.org/wiki/Correlation_database - a database management system (DBMS) that is data-model-independent and designed to efficiently handle unplanned, ad hoc queries in an analytical system environment. Because a correlation DBMS stores each unique data value only once, the physical database size is significantly smaller than relational or column-oriented databases, without the use of data compression techniques. Above approximately 30GB, a correlation DBMS may become smaller than the raw data set.

Relational





  • https://en.wikipedia.org/wiki/Relational_calculus - consists of two calculi, the tuple relational calculus and the domain relational calculus, that are part of the relational model for databases and provide a declarative way to specify database queries. This in contrast to the relational algebra which is also part of the relational model but provides a more procedural way for specifying queries.


  • https://en.wikipedia.org/wiki/Relational_algebra - first created by E.F. Codd while at IBM, is a family of algebras with a well-founded semantics used for modelling the data stored in relational databases, and defining queries on it. The main application of relational algebra is providing a theoretical foundation for relational databases, particularly query languages for such databases, chief among which is SQL.



  • etc.




Object


SQL

ugh





SELECT * from table;









  • SQL-DK – an batch/terminal client for relational databases


MySQL

MariaDB is compatible with MySQL, you probably want to use that, if not Postgres





  • YouTube: MySQL - A series covering working with MySQL including managing databases, tables and data.

Connecting

mysql -p
  # connect with anonymous user, prompt for password
mysql -u username -ppassword -h nonlocalhost dbname
  # specify user, password and nonlocalhost address, USE dbname



Admin


mysqladmin - a client for performing administrative operations. You can use it to check the server's configuration and current status, to create and drop databases, and more.



SHOW engines;

SHOW processlist;

Show variables;

Database management

SHOW databases;
USE [db name];
CREATE DATABASE [dbname];
mysql -u username -p -e "CREATE DATABASE dbname CHARACTER SET utf8 COLLATE utf8_general_ci";
  # drupal 7
select database();
  # show which database is in use
DROP database dbname;
  # remove dbname from db;

User management


CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'newpassword';


SELECT User FROM mysql.user;
  # show all database users


USE mysql;
SET PASSWORD FOR 'user-name-here'@'hostname-name-here' = PASSWORD('new-password-here');
UPDATE mysql.user SET Password=PASSWORD('new-password-here') WHERE User='user-name-here' AND Host='host-name-here';


Passwords
SET PASSWORD FOR 'user'@'localhost' = PASSWORD('mypass');
mysqladmin -u user_name -h host_name password "newpwd"


Password=PASSWORD('NewPassword') WHERE User='root'; FLUSH PRIVILEGES;


Permissions


SHOW GRANTS;
  # show permissions for current db user
SHOW GRANTS FOR user@localhost;
  # show permissions for a user
SELECT CONCAT("SHOW GRANTS FOR '",user,"'@'",host,"';") FROM mysql.user WHERE host!='localhost';
 # Create command list for showing user grants [8]


GRANT all on [dbname].* TO '[username]'; [9]


GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES ON databasename.* TO 'username'@'localhost' IDENTIFIED BY 'password';
  # drupal 7
create database wikidb;
grant index, create, select, insert, update, delete, alter, lock tables on wikidb.* to 'wikiuser'@'localhost' identified by 'password';
#mediawiki??


REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ...


FLUSH privileges;
  # Reloads the privileges from the grant tables in the mysql database.

The server caches information in memory as a result of GRANT, CREATE USER, CREATE SERVER, and INSTALL PLUGIN statements. This memory is not released by the corresponding REVOKE, DROP USER, DROP SERVER, and UNINSTALL PLUGIN statements, so for a server that executes many instances of the statements that cause caching, there will be an increase in memory use. This cached memory can be freed with FLUSH PRIVILEGES.

Table management

SHOW tables;

SELECT * from mysql.user;
  # return ascii table with rows from user table from mysql database

SELECT * from mysql.user\G;
  # return vertical row information from user table from mysql database
pager less -SFX
  # info will now be returned via less, use arrow keys to navigate large tables, q to quit this mode
nopager
  # reset output from pager to stdout
SELECT table_schema "Data Base Name", sum( data_length + index_length ) / 1024 / 1024 "Data Base Size in MB" FROM information_schema.TABLES GROUP BY table_schema ;


13.8.1. DESCRIBE provides information about the columns in a table.


Troubleshooting


Backup and restore

If your tables are primarily InnoDB tables, or if you have a mix of InnoDB and MyISAM tables, consider using the mysqlbackup command of the MySQL Enterprise Backup product. (Available as part of the Enterprise subscription.) It provides the best performance for InnoDB backups with minimal disruption; it can also back up tables from MyISAM and other storage engines; and it provides a number of convenient options to accommodate different backup scenarios. See Section 25.2, “MySQL Enterprise Backup”.

If your tables are primarily MyISAM tables, consider using the mysqlhotcopy instead, for better performance than mysqldump of backup and restore operations. See Section 4.6.9, “mysqlhotcopy — A Database Backup Program”.

mysql < database.sql
  # if database file was saved with CREATE DATABASE
mysql databasename < database.sql
  # specify database name to import database file
mysqldump
mysqldump [options] db_name [tbl_name ...]

mysqldump [options] --databases db_name ...

mysqldump [options] --all-databases


mysqldump -u username -p --all-databases --routines > outputfile.sql
mysqlbackup

Install the mysql-client package to access.

For a non-busy server;

mysqlbackup --port=3306 --protocol=tcp --user=root --password --backup-dir=/home/user/backupdir backup-and-apply-log

Replication

Tools

  • dBug - "PHP version of ColdFusion’s cfdump. Outputs colored and structured tabular variable information. Variable types supported are: Arrays, Classes/Objects, Database and XML Resources."
  • anywhereindb - Sometime we need to find out a small piece of string in big Database. Like where is the configuration is saved, or where is Jon's Date of birth is saved. This code is search all the tables and all the rows and columns in a MYSQL Database. The code is written in PHP. For faster result, we are only searching in the varchar field.

Scripts

./searchreplacedb2cli.php --host localhost --user root --database test --pass "pass"
     --charset utf\-8 --search "findMe" --replace "replaceMe"
--dry-run

Performance

Clients

phpMyAdmin
Other web
wget http://www.adminer.org/latest-mysql-en.php -O adminer.php
wget http://www.adminer.org/latest-en.php -O adminer.php

MariaDB

Fork of MySQL, drop in replacement.

SQLite

PostgreSQL

Ingres

Other

IBM DB2

Oracle Database

IBM System R

NoSQL


dbm

Redis

See also Server#Redis

Used in the BOA stack for caching.

CouchDB

Couchbase

MongoDB

JavaScript

MDBM


Other



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  • Trousseau is a gpg encrypted key-value store designed to be a simple, safe and relient place for your data. It stores data in a single multi-recipients encrypted file and can supports both local and remote storage sources (S3 and ssh so far) import/export.

gpu;


Graph

Replication

  • http://www.symmetricds.org/ - open source software for database and file synchronization with Multi-master replication, filtered synchronization, and transformation capabilities. It is designed to scale for a large number of nodes, work across low-bandwidth connections, and withstand periods of network outage. Data synchronization occurs asynchronously from a scheduled job, with data changes being sent over a push or pull operation.
  • https://en.wikipedia.org/wiki/SymmetricDS

Distributed

Social

Other