SQL exercises
January 17, 20:07 MSK


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Would you get the following certificate?
Yes 69.2%
No 11.2%
Probably I would get it for supporting the project 9.5%
Such certificate is unnecessary one 5.6%
Such certificate is necessary on a site, but not for me 4.5%

Total Votes: 34924


Author Comment            page [1] 2 3 4
Dvoryaninov Victor,
Business analyst at CJSC "VTB Capital" (Moscow),
I.B.Tleukenov (Rokford),
MSc in Business Engineering (Novosibirsk),
Few days ago Ive solved last exercise of first rating stage, so I get my first certificate Basic knowledge on sql-ex. I will want to describe my feelings of interaction with site.
4 october 2014 I started to learn basic of database theory and SQL. My knowledges in this direction were empty. In my opinion, sql-tutorial and leaning stage are the best for beginner. I spent three month to solve all exercises of leaning stage.
I like rating system on first rating stage. When I performed my goals I founded another users on a site they had same scores and time solution, so I started to compete with them. It was amazing. I have solved all exercises on first stage in one month.
Thanks to creators and authors of exercises!
Also special thanks qwrqwr for unusual cases.
Kobelyatskyy Mykhaylo (kiiki),
MSc in Financial Economics (Lund University),
I accidentally saw SQL-EX and solved a couple of exercises on the learning stage. I didn't have any previous experience with relational databases and I think that I was caught on simplicity of initial tasks and clarity of explaining articles. But as I went further I became more and more interested in the subject and after I had obtained the first certificate, I decided to strive for the second one. Now I have both, but I am still tempted to proceed when I see next unsolved exercise.
The process of education is extremely interesting and addictive. Some of the exercises are pure masterpieces. Many of them require not only solid T-SQL skills, but also building of sophisticated logical algorithms and conducting mathematical computations. The data manipulation techniques that I learned here allow me to perform for several seconds operations that were unrealizable or took lots of time in Excel. You get used to work with all possible types of data, learn how to cope with gaps and inconsistencies in databases structure, become proficient in twisting, stacking and joining tables in absolutely crazy ways. Moreover you can extend your skills by adopting methods of other participants.
I want to thank creators of this site, technical support and all amazing people here who create unique atmosphere of friendly intellectual competition. I am really proud to be a part of this community.
As a person who didn't have any relation to programming but found this site extremely useful, I would primarily like to recommend it to quantitative and data analysts of all kinds. I think that SQL-EX will also be very helpful for people who want to become programmers but are not sure what niche to choose. Knowledge of SQL and relational databases can be both good addition to another programming languages and self standing specialization. So I encourage everybody to prove your skills. But beware, once you get a flavour of it - it may be impossible to stop.
Jimmy Tan (kof1979),
Software engineer (Singapore),
Dear SQL-Ex Team, I am a software engineer from Singapore. Before I found this website, i though my SQL was better than average. Until I started SQL exercises then I realised how weak my SQL was. I am extremely excited for learning so many "amazing" skills. These skills are very practical and cannot be easily found in books. Thanks for all the effort for creating and maintaining such a great site! I wish all the best to sql-ex and express my gratitude from the other side of the world from. Thanks!
Vladislav Bryzgunov (lorins_),
programmer at Rombo-projects, Ltd (systems integrator),
I registered on this site about a year ago. Before that my knowledge of SQL just let me join two tables using JOIN statement. And even then I used Access Query Builder for the most part. Implementing of all business logic in my company software required skills of working with Recordset objects (DAO, ADO).
When solving problems on this site Ive got an invaluable experience of building SQL queries. Once I rewrote one of modules of a pricing application using my new knowledge. The result exceeded all expectations. The time of procedure execution decreased by hundreds of times! I think it speaks for itself. I think that certain IT professionals need not only to have an idea of SQL but to know it.
There are no projects as good as SQL exercises. Of course, they may exist, but this project is a unique one. It offers practical work which let students to acquire a deep and working knowledge. There is another benefit. Solving the problems of SQL-EX at least supports mental abilities (yes, yes, they become weaker eventually) and even develop them. Many exercises are hard, and one has, as they say, to rack his brains over the solution. I have felt again like a school boy, sent to a competition on mathematics :)
It should be noted that a lot of interesting and smart people are present at the site forum. Its atmosphere is warm and friendly. Contentious issues cause a discussion, not a dispute nor outright insults, like on some forums (guess which :)).
So, I say great thanks to the SQL exercises team. Especially I thank the project head Sergey Moiseyenko.
Dmytro Boiko (Angellore),
BI Consultant at BITerra s. r. o.
Kyiv, Ukraine
My acquaintance with site sql-ex began four years ago when I started to work. One of my friends told me, when you solve one hundred tasks you will become a good specialist. So I started this trip. And I was not disappointed! Because:
1. solving tasks at sql-ex is very efficient: after solving the problem it is possible to see how other guys solved it;
2. support and the people are very friendly;
3. rating system really motivates.
I want to thank all developers of the site and all those who helps to develop such a wonderful resource that can be used not only for teaching but also for leisure.
Dmitriy Sabitov (railgun3r),
Goverment Organization "Territorial fund of information on Natural Resources and Environment Protection of the Republic of Komi", specialist (entry level programmer),
As a participant of third stage, who "fit" at the 31 th position (this is not the end XD) in the TOP100 and who resolved exercise number 143 (most rated among all exercises), I also would like to write a few words of appreciation project.
Firstly, when I first got into web-address bar "sql-ex.ru" I did not know about SQL practically nothing (Perhaps only the basic operators). I struggled with the learning phase for several months. I read the forum, I pestered tech support, asking for tips on difficult tasks. Only because it was terribly interesting to solve ingenious puzzles. And because I wanted to prepare to pass the exam in college. Then I even managed to perform tasks on rating stage (1'st and 2'nd) and get the Basic Requirement sertificate. However, in the end, I accidentally slept through an exam. *fail* ))), but it does not matter ...
It is important that this project really helped me. I learned about "sql-ex" by a fluke. "sql-ex" helped me learn how to write queries of any complexity. In fact, it was just fun to write sql-queries. Though, I thought that these skills (construct most hardest sql-queries) obviously don't need in my life. Because SQL is normally used only for simple selections from tables of local DB or web-DB. NOTHING OF THE KIND!!! As soon as I got a job "entry-level programmer" I understand how important is it to construct most hardest sql-queries. Often I am asked to write a crazy sql-queries with a mix of a dozen tables, with a variety of tricky partitions, etc... (Just for reporst or something else...). Often when I working it is necessary to use methods like "For XML Path", "XML nodes", etc. These methods have the documentation, but they are very rare in the tutorial books. In the exercises on this site, these methods are very common.
In general, whole-heartedly thank the project and all who support and develop.
Kuznetsov Vitaliy (herrRo),
"Everything about accounting" newspaper`s editorial staff (Kiev, www.vobu.ua), DB programmer,
Perhaps, I am the one of the small group of people who had become to the sql-ex having only basic skills in SQL and have gone to the top of the rating. I had just changed my place of employment and I must re-train to an Oracle database programmer from an applied programmer mainly working with OpenGL on Delphi. It was impossible without confident knowledge of SQL. Then my senior colleague had told me about site with many intricate tasks to train on and also to gain a certificate, which helped my predecessor to get another job. "When the interviewer have known that the candidate owns an sql-ex certificate he wouldn`t ask any questions in SQL". I have clearly remembered his words that day.
I had received a task to get 150 points in two weeks. And I had made it, by solving tasks, reading FAQs, manuals and hints, and also by passing the learning stage. I had fulfilled the conditions of the BK certificate. After that I had approached to the "very difficult task", as I think, and I surrender. But in this time already I realized the educational power of this project. After two years I have returned to the site and see that I was creating very inefficient solutions. And then I feeled motivation to prove myself that I become "cooler". I had solved that task. And then I had solved next, and next. But there are too many tasks. And I decided to continue solving until I face task that I cannot solve.
I have never faced it. But from moment when I was solving "very difficult" 18th task (with no idea about what ranking function is) and to now, some strange transformation occurred. The notion of difficulty is moving back from me. It is difficult to aggregate symbolic expressions in one row? Do two- and three stage rankings? Calculate some sums with progressive total? Easy! The question in what one from algorithms is simpler readable and more effective.
When I had faced some "difficult" task, I was frightening by thought that there will more difficult tasks. Now I understand that it is great, because the solving of the next task makes the previous one simple and clear. For that I thank all of the authors and developers of SQL-ex, and the great site`s community also.
The site is absolutely unique, fully-fledged, completely free, and it is in advance. Good luck =)
Author Comment            page [1] 2 3 4

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