How can I go further on with SQL ?

Question

SQL skills

Answer 1

practice basic queries by create simple database

Answer 2

My advice is to practice thoroughly with joins (either inner or outer), exists, not exists, group by's and aggregate functions. I can say they're widely used.

Answer 3

Know to write procedures, joins, using triggers, Views..
U can find sample dump files or backups in internet.. Practise on them..
Know the different platforms and the differences in usage. e.g MySQL, Oracle