you can further define database that use SQL as relational databases. The only other type of databases I've heard of were Object oreinted databases, but they never gained market share.
also, you could further define the SQL language as Transact SQL or T-SQL for short.
DBA Skills (including but not limited to)
creation and placement of database and transaction log files.
index tuning
query tuning
linking servers
server replication
creating maintanence plans
edit - i see that the job is not a dba job. in this post, i wanted to show that SQL databases are complex systems.