This site will help everyone to gain or improve skills in building
SQL Data Manipulation Language statements. To train You will have to build yourself
the SQL statements for retrieval or modification of specific data required in the exercises.
When Your query is incorrect, You will be able to see rows returned by the correct
query along with that returned by Your query. Furthermore, you may execute arbitrary
DML statements on available databases by setting the "Without checking" option. There are
four levels of difficulty (from 1 to 4), You may see it in second column of
exercises list. We propose the exercises on retrieving data (SELECT statement) and
the exercises on modifying data (INSERT, UPDATE, and DELETE statements).
Your success in the solving the exercises are shown by a rating of participants.
As this takes place, there are three stages:
the first one (first 21 exercises) is performed without time control for an individual
exercise, the second one (begins with the exercise #22) controls time for completion of each
task. At the third stage which refers to optimizing and
begins with exercise #139, it is required not only to solve an exercise
correctly, but also time of execution of inquiry should be
commensurable with time of execution of the author's solution.
Exercises of the first stage are available without registration and may be solved
in any order You like. The solution of the rest of exercises requires registration.
REGISTRATION IS FREE as this for all other services of the site. In the third column of exercises list You
will be able to see ("OK") notes with the numbers of done exercises, but that
is available only to the registered users. In fact, that is the main reason for registration.
If You would like to visit our web site again, You won't have to recollect which
exercises You have done already and which You haven't. If You don't want to register,
You may enter as a guest, but in that case Your results won't
be traced by the system. Registered users also may discuss the solutions to exercises in our forum.