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RDBMS (Relational Database Management System) Relational Database Management system

What is the database:

Database (Database) is a warehouse that organizes, stores and manages data according to the data structure. Each database has one or more different API to create, access, manage, search and copy the saved data.

The so-called relational database is a database based on the relational model, which deals with the data in the database with the help of mathematical concepts and methods such as set algebra.

RDBMS is the characteristics of relational database management system (Relational Database Management System):

The data appears in tabular form.

Various record names for each behavior

The data field corresponding to the record name of each column

Many rows and columns form a form

Several forms make up database

RDBMS terminology

Before we move on to the MySQL database, let's take a look at some of the terms of RDBMS:

Database: a database is a collection of associated tables. .

Data table: a table is a matrix of data. A table in a database looks like a simple spreadsheet.

Column: a column (data element) contains the same data, such as postcode data.

Row: a row (= tuple, or record) is a set of related data, such as a piece of data that a user subscribes to.

Redundancy: twice as much data is stored, redundancy reduces performance, but improves data security.

Primary key: the primary key is unique. There can be only one primary key in a data table. You can use the primary key to query data.

Foreign keys: foreign keys are used to associate two tables.

Compound key: compound key (compound key) uses multiple columns as a single index key, which is generally used for composite indexes.

Indexes: use indexes to quickly access specific information in database tables. An index is a structure that sorts the values of one or more columns in a database table. A catalogue similar to a book.

Referential integrity: referential integrity requires that references to entities that do not exist are not allowed in the relationship. And entity integrity is the integrity constraint that the relational model must meet in order to ensure the consistency of the data.

MySQL is a relational database management system developed by MySQL AB Company of Sweden and currently belongs to Oracle Company. MySQL is an associated database management system that stores data in different tables instead of all data in a large warehouse, which increases speed and flexibility.

System characteristics:

1. Written in C and C++, and tested with a variety of compilers to ensure the portability of the source code.

2. Support AIX, FreeBSD, HP-UX, Linux, Mac OS, NovellNetware, OpenBSD, OS/2 Wrap, Solaris, Windows and other operating systems.

3. API is provided for many programming languages. These programming languages include C, C++, Python, Java, Perl, PHP, Eiffel, Ruby,.NET and Tcl.

4. Support multithreading and make full use of CPU resources.

5. The optimized SQL query algorithm can effectively improve the query speed.

6. It can be used not only as a separate application in the client server network environment, but also as a library and embedded in other software.

7. Provide multi-language support. Common codes such as GB2312 and BIG5 in Chinese and Shift_JIS in Japanese can be used as data table names and data column names.

8. Provide a variety of database connections such as TCP/IP, ODBC and JDBC.

9. Provide management tools for managing, checking, and optimizing database operations.

10. Support large databases. It can handle large databases with tens of millions of records.

11. Multiple storage engines are supported.

12.MySQL is open source, so you don't have to pay extra.

13.MySQL uses the standard SQL data language form.

14.MySQL has good support for PHP, and PHP is the most popular Web development language at present.

15.MySQL can be customized, using the GPL protocol, you can modify the source code to develop your own MySQL system.

16. Online DDL/ change capabilities, data architecture support for dynamic applications and developer flexibility (5.6 [3] added)

17. Copy the global transaction identity to support self-healing clustering (5.6 [3] added)

18. Replication has no crash slaves, which can improve availability (5.6 [3] added)

19. Copy multithreaded slaves to improve performance (5.6 [3] added)

Storage engine:

The default database engine prior to MyISAM MySQL 5.0is the most commonly used. Has high insert and query speed, but does not support transactions

The preferred engine for InnoDB transactional database, which supports ACID transactions and row-level locking. MySQL 5.5 has become the default database engine.

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