Practical Skills Of SQL Language

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.

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