relational database
The first independent RDBMS introduced is MySQL. I believe most of my friends are already very familiar with MySQL. Basically, the growth history of MySQL is the growth history of the Internet. The first MySQL version I came into contact with was MySQL4.0, and later MySQL5.5 was more classic-almost all Internet companies used it. MySQL also popularized the concept of "pluggable" engine. Choosing different storage engines for different business scenarios is an important way to tune MySQL. For example, using InnoDBMyISAM for scenarios with transaction requirements may be suitable for concurrent reading scenarios; But now I recommend InnoDB in most cases. After all, 5.6 has become the official default engine. Most of my friends basically know what scenarios MySQL is suitable for (almost all scenarios that need persistent structured data), so I won't go into details.
It is also worth mentioning that MySQL5.6 introduces multithreading replication and GTID, which makes fault recovery and master-slave operation and maintenance more convenient. In addition, version 5.7 (currently GA version) is a major update of MySQL, mainly because the reading and writing performance and replication performance have made great progress (version 5.6 has achieved parallel replication at SCHEMA level, but it is of little significance, but MariaDB's multi-thread parallel replication shines brilliantly, and many people choose MariaDB because of this feature. MySQL5.7MTS supports two modes, one is the same as 5.6, and the other is multi-thread replication based on binloggroupcommit, that is, binlog submitted at the same time at the main end can also be applied at SLE end to realize parallel replication). If you have friends who choose stand-alone database technology, you only need to consider 5.7 or MariaDB, and after 5.6 and 5.7 are taken over by Oracle, the performance and stability have been obviously improved.
A database system
PostgreSQL has a very long history. Its predecessor was Ingres of UCB, and MichaelStronebraker, who presided over this project, won the Turing Award in 2023. Later, the project was renamed Post-Ingres, which is based on the open source under BSDlicense. 1995, several UCB students developed the post-Ingres SQL interface, officially released PostgreSQL95, and then grew up step by step in the open source community. Like MySQL, PostgreSQL is an independent relational database, but unlike MySQL's SQL syntax, PostgreSQL's SQL support is very powerful. PL/SQL is much more powerful than MySQL in built-in types, JSON support, GIS types and support for complex queries, and the code quality of PostgreSQL is better than MySQL in terms of code quality. In addition, compared with the version before MySQL5.7, PostgreSQL's SQL optimizer is much more powerful than MySQL, and almost all slightly complicated queries perform better than MySQL.
Judging from the trend in recent years, PostgreSQL is also very strong. I think the disadvantage of PostgreSQL is that it doesn't have a strong community and mass base like MySQL. After so many years of development, MySQL has accumulated a lot of operation and maintenance tools and best practices, but PostgreSQL, as a rising star, has better design and richer functions. Computer training found that the version after PostgreSQL9 is stable enough, which is a good choice when choosing new project technology. In addition, many new database projects are secondary developed based on PostgreSQL source code, such as Greenplum.