One, why should learn database
The ability to react to the business and quickly analyze and locate problems
will encounter many problems in software development. In the final analysis, it is a problem with data in the database. For example, we have to verify whether the source of registration is correct, if we don’t check the database. , I don’t know the existence of this field. Although it says such a paragraph in the requirements, when I actually do a functional test from the page, I can’t see whether the registration source is correct or not, so we have to go Look at the database.
Two, common databases
1. Relational database
Relational database: The official explanation of the relational database is more difficult to understand. To put it simply, a relational database is an organizational structure that stores data in the form of rows and columns, which is embodied as a two-dimensional table. And there may be some relationships between multiple tables.
1.1.
Oracle Oracle is a set of software products with distributed database as the core provided by the American oracle company (Oracle). The characteristics of oracle database are security, high speed, stability, and good concurrency. These characteristics make many large enterprises choose databases. When I did not hesitate to choose oracle.
In the early years, almost 100% of the Fortune Global 500 were Oracle users. But oracle is charged and not cheap. This also makes many start-ups or small and medium-sized enterprises completely unable to afford the expenses, and instead of using oracle, choose simple and easy-to-use, lighter and free and open source MySQL.
1.2.
MySQL MySQL is a relational database management system that develops source code, and is favored by small and medium-sized enterprises because of its speed, reliability and applicability. Although the earlier version does not support functions such as transaction operations, subqueries, foreign keys, stored procedures, and views.
But since the 4.0beta version released in 2002, innoDB has been used as the default engine outside MySQL, which greatly improves transaction processing and data caching capabilities. The 5.0 version in 2005 has added stored procedures, server-side cursors, and triggers. Server, query optimization, and distributed transaction functions.
1.3.MariaDB
MariaDB database is a branch of MySQL and is maintained by the open source community. Part of the reason for developing MariaDB is because of concerns that after Oracle acquires MySQL, there will be an intention to close MySQL. Therefore, the community adopts branching to avoid this risk. .
MariaDB is fully compatible with MySQL, including API and command line. It is a perfect substitute for MySQL. In terms of storage engine, MariaDB uses xtraDB instead of MySQL's InnoDB.
1.4.
Sqlserver Sqlserver is a database developed and promoted by Microsoft. It was originally jointly developed by Microsoft, Sybase and Ashton-tate, and the first OS/2 version was launched in 1988.
Ms SQL server is mainly for small and medium enterprises. Its biggest advantage is that it integrates various products and resources of Ms, provides a powerful visual interface, highly integrated management and development tools, and has considerable achievements in the rapid construction of business intelligence (BI).
2. Non-relational database
non-relational database: The data structure of a non-relational database is completely different from that of a relational database. It mainly stores data in the form of key-value pairs.
2.1.
Memcached Memcached is a software developed by Brad Fitzpatric of Danga Interactive, a subsidiary of livejournal. Its emergence can solve a series of database bottlenecks. Because frequent and centralized access to the database in web applications will bring A series of problems caused by high concurrency.
For example, problems such as increasing the burden on the database, deteriorating response, and delaying website display, etc., but with the data caching mechanism provided by memcached, these problems are not a problem.
2.2.
Redis Redis is a key-value storage system. Similar to memcached, it supports relatively more value types, including string (string), list (linked list), set (collection), and hash (hash type). Redis is a high-performance key-value database.
The emergence of Redis has largely compensated for the inadequacy of key/value storage such as memcached, and in some cases can play a good supplementary role to relational databases.
2.3.
MongoDB MongoDB is a product between relational databases and non-relational databases. It is the most versatile and most like relational database among non-relational databases. The data structure he supports is very loose, it is a bson format similar to json, so the course stores more complex database types.
The biggest feature of Mongo is that the query language it supports is very powerful. Its syntax is a bit similar to an object-oriented query language. It can almost all realize most of the functions similar to relational database form queries, and it also supports indexing the database.
Three, how to learn database
1. Create/delete library, create/delete table, view library, view table
2. Backup, restore data
3. Stored procedure, view
4. Import and export data
5. Basic database configuration: modify password, add user, etc.
6. Database Link tools: such as WorkBench Navicat phpMyAdmin, etc.
7. Basic addition, deletion
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modification and query statement 8. Slightly more complicated SQL: multi-table query, sub-query, etc. 9. At least you must know the common database: Mysql MSSQL Oracle Memcached Redis Mongodb
10. Database Installation and deployment: You must at least be able to install the number on the server or your own computer