SQL is very interesting one. Once you start with simple queries you will be find it easy and simple.
Plenty of good websites available for SQL queries. So start from the beginning level use the below links.
Once to cross the beginner level then you can start checking on this website, which is one of my favorite too.
All the Best!!!
SQL (Structured Query Language) is a standard interactive and programming language for getting information from and updating a database. Although SQL is both an ANSI and an ISO standard, many database products support SQL with proprietary extensions to the standard language
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Microsoft MVP 2014 [ASP.NET/IIS]