The MySQL system administrator is a very specialized niche, even expert knowledge about it may not be enough to find a job. Although any expert in the field of MySQL knows quite a lot about related technologies. You also have to learn a lot that is not directly related to MySQL.
Immediately I want to warn about the pitfall: due to the "watered-economic" reasons, MySQL will soon surrender its positions in the IT community. The fact is that due to a series of mergers, the DBMS was in the hands of Oracle Corporation. Considering that InnoDB was built as a less expensive replacement for Oracle, this is not very good for the future development of the DBMS. In this regard, it is hardly worth expecting the rapid development of official MySQL in the near future (or at least the pace of development of the sample of 2007, the DBMS openly stagnates). There are alternative companies that are developing technologies based on MySQL - MariaDB, Percon, they should pay close attention. However, it is better not to focus only on MySQL, also study PostgreSQL, Oracle, MS SQL, NoSQL solutions. It will protect you great in the future employment.
If I did not dissuade you from focusing on MySQL, you should pay attention to the following points (in fact, there are many more of them, I will list only a part):
- operating systems: it is necessary to study * nix-systems in all manifestations, since most installations will be on UNIX-like operating systems. Knowledge of operating systems and the ability to administer them will be useful to you in your work more than even knowledge of MySQL; It would be nice to know bash, vim, sed, awk, the subsystem of access rights and modifications in modern distributions;
- logging - syslog, nagios, zabbix, etc .;
- replicate, install multiple virtual machines (VirtualBox, vagrant) and experiment. Replication in MySQL is rather capricious and often fails. The more experience you have with her, the better; Replication serves as the basis for scaling up and reliable backup - it is better to remove copies of databases from a cold replica than from a busy server, ALTER queries are performed for days in a heavy database, in general you will have to master replication. Binary logs are also part of the replication mechanism.
- monitoring, also mostly refers to nix *.
Two great books have been translated into Russian.
- MySQL Performance Optimization. Baron Schwartz, Peter Zaitsev and others. Symbol plus, 2010.
- Ensuring high availability of systems based on MySQL. Charles Bell, Mats Kindal, Lars Tallmann. Russian edition, BHV, 2012.
It would be nice to get acquainted with them. Ideally, get acquainted with all the new literature, published in English.
There is another caveat: working as a system administrator, there is a great temptation not to write code or participate in application development. It would be nice to encode at least a little bit in order to “feel” the applications and navigate the complexity of certain solutions on the developer’s side. To do this, you need to master at least one scripting language (not bash / perl, better if it is python). His knowledge is useful for solving administrative tasks.