List of 5 Best SQL Learning Resources IMHO
Without the words about importance SQL and its popularity, I start my list. Please, keep in mind that this is list, not top. All the resources mentioned below are worth and have their own features.
(challenging option, not for beginners)
One the best place for SQL training and get certified is HackerRank. This is free plarform which allows you to train your skills in building up databese queries. The challenges are devided into levels (from easy to hard) and main topics. It makes training more logical and complex.
SQL challenges page
All the challenges can be done in browser, so there is no need to downlod anything.
Hacker Rank Interface
Moreover, there is a Discussion tab. So if the challenge looks hard for you or you don't understand where the problem in you query is, you can use this tab to look for hints or even full correct queries.
Hacker Rank - Discussion Tab
(good for beginners)
I would say that SQLZoo is more academic resource. It also covers main SQL topics and syntax, but also teoretically explains and demonstrates how it works. SQL has an opportunity for learner not to build up the query starting from empty field, but to modify it, step by step making the challenges more complicated.
SQLZoo Challenge Example
SQLZoo has also challenge page with video answers and explanations.
SQLZoo Challenge Example
From my point of view SQLZoo is a good place to learn SQL, but not to train it. For me it is too academic, there are not so many challenges and they are too easy.
Another educational resource that can be fully passed in browser, without useless downloads.
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For me, SQLBolt is a good start for those who has no idea what SQL is and why it exists. Resource is full of academic information and covers all the basic topics (like all the resources I mention here).
SQLBolt Start Page
However, for me there is so many text and few examples, real examples to illustrate the theoretical parts.
In our subreddir (r/becomingnerd) I didn't see any bad reviews about this resource from the beginners, only positive ones.
(nice for interview preparations)
Another resource with witty name. I like this one, because it presents real interview challeges while hiring from well known companies.
DataLemur Start Page
There is also level splitting, progress graph, main SQL topics to cover.
All DataLemur Challenges Page
The thing that I love about about DataLemur is that difficulty levels correlates with the real tasks difficulty. I mean, if it is written that the challenge is easy, it will be easy. Yes, it is crucial (for example, for the next resource this advantage is not related).
DataLemur Challenge Example
I would recommend DataLemur for those who are hiring and know that on the inteview there will be SQL part, for those who want to refresh SQL after many month of not using (like I did).
I wouldn't recommend it for beginners. The challenges for them could be rather difficult and it's better to find smth with theoretical blocks or tutorials.
(great material presentation)
This was my first online training platform amoung the other ones. There are a lot of challenges, challenges that covers all the main topics. There is a great documentation, so you don't need any other web sites to look for hint.
However, sometimes difficulty levels don't correlates with the real tasks difficulty. Sometimes, the challenge with 7 difficulty level easier that the challenge with 4 diffuculty level.
SQL Academy Challenge Page
Unfortunately, SQL Academy is not beginner frienfly. There is no other options to get hint or answer except buying premium account. So, the only thing you can do is to look for documentation on Guide page. It's not bad, but sometimes documentation is not full and you just waste your time.
SQL Academy Guide Page
In general, this a good variant with rather challenging tasks, but be ready to google in case you need a hint.
If I start over learning SQL, I would choose SQLBolt, because there is enough information for beginner and it is presented well (not perfect, but well), then I would choose something more challengingt, like SQL Academy or SQLZoo. Then, to get cerified I would use HackerRank and finally prepare for the interview on DataLemur.
I would definetly pass through all of them, despite the fact that they are very familiar.
The last thing I want to say - Good luck. It is possible to learn SQL in a month ob a good level. So, take your time.