Whether working with MySQL, MSSQL or Oracle databases, beginning SQL server developers should pay close attention to security, how to form the most efficient SQL queries, how joins work, and that proper permissions are implemented for all user accounts. SQL servers of all types are used for most modern websites.
Any code on a website that communicates directly with a SQL server must be properly secured against attacks. If it is not, attackers can design attacks against the code that exploit the vulnerabilities to gain direct access to the SQL server and all of the data stored on it. Likewise, all SQL server accounts should be properly designed to only access the specific databases and tables that they need. That way, if an account is ever compromised, the amount of data at risk is minimized.
Efficiency is paramount when writing good code for a SQL server. Queries that search across an entire database and use a generic query cause significant slowdowns in the server, and can cause it to become unstable and unresponsive. This is especially true in situations where two or more tables must be queried in conjunction with each other. In these cases, the proper use of join statements is vital, and can make a huge difference in the performance of a SQL server.