Computer Science & Engineering vs HelloSQL

Computer Science Engineering puts a complete CSE course in your pocket: 84 subjects, 425 tutorials and 8,891 lessons covering the full computer science and engineering syllabus, in plain language. Revising for an exam, preparing for a technical interview, or starting from scratch? Every core subject is here, and all of it works offline. WHAT YOU WILL LEARN Data Structures and Algorithms — arrays, linked lists, stacks, queues, trees, graphs, hash tables, sorting, searching, greedy methods, dynamic programming and complexity analysis. Database Management Systems — relational models, SQL, normalization, ER diagrams, transactions, indexing and an introduction to NoSQL. Operating Systems — processes and threads, CPU scheduling, deadlocks, memory management, virtual memory, paging and file systems. Computer Networks — OSI and TCP/IP models, routing, switching, IP addressing, subnetting, HTTP, DNS and network security basics. Computer Architecture — processor design, instruction sets, pipelining, cache memory, memory hierarchy and I/O systems. Programming — core concepts with worked examples in C, C++, Java and Python, plus object oriented programming, recursion and exception handling. Software Engineering — development life cycle, agile methods, testing strategies, design patterns and version control. Theory of Computation and Compiler Design — automata, regular languages, context free grammars, lexical analysis, parsing and code generation. PRACTICE, NOT JUST READING 26,874 quiz questions covering every subject. Each session is ten questions with four options and a timer, drawn from the chapter you have been studying. Three difficulty levels: beginner 30 seconds per question, intermediate 20, expert 10. A full session runs 5:00, 3:20 or 1:40. Pass at 70% or above. Filter by level, by what you have attempted, and by your best score, so revision targets your weak subjects. Every attempt is saved to your history. INTERVIEW PREPARATION 25 technical interview roles with 100 questions each — 2,500 in total — built around what campus placements and technical interviews actually ask. Same timed format, same pass mark, same saved history. STUDY OFFLINE Download any subject for offline reading. Lesson text is stored on the device, so the syllabus stays available on a bus, in a lecture hall, during a power cut, or anywhere mobile data does not reach. Images still need a connection. Opened lessons are cached automatically, so anything you have already read stays readable even if you never hit download. The Downloads screen shows what is stored, how much space it uses, and lets you cancel, resume or remove any subject. TRACK PROGRESS, EARN A CERTIFICATE Mark lessons complete and watch the progress percentage climb on every subject. The Continue card on the home screen drops you back exactly where you stopped. A daily reading streak counts every day you study, with an optional reminder that is off by default. Complete every lesson in a subject and pass its quiz at 70% or above to unlock a certificate you can save and share. BUILT FOR HOW STUDENTS STUDY Short sections you can finish in a few minutes. Syntax highlighted code with one tap copy. Search across the whole syllabus. Bookmarks and history. Light, dark and system themes, adjustable font size, and a choice of where the previous and next buttons sit. Proper tablet layouts, not stretched phone screens. WHO IT IS FOR CSE students revising for exams, candidates preparing for competitive examinations and campus placements, developers refreshing fundamentals before interviews, and career changers moving into software. Frameworks change every year. Data structures, algorithms, operating systems and networking do not. No video to buffer. No account to create. Open your first tutorial in under a minute. Questions, corrections or a topic request? Email mail@ehsanur.com — we update the app based on what learners ask for.

SQL tends to make sense while you're reading about it, then fall apart the moment you try to write it yourself. HelloSQL is for the writing part. You read a problem, write a query, and run it. The results show up as a table, and if they're right, it's marked correct right away. Grading looks at what your query returns, not how it's written, so your query doesn't have to match ours. There are 120 exercises, and most of them look like everyday reporting tasks. For example: "List payments from largest to smallest. If two amounts are the same, put the older one first." The practice data is built around an online store's orders, employee attendance, and billing for a subscription service. What's free and what isn't The first 30 exercises are free, and you don't need an account. They cover SELECT, WHERE, ORDER BY, and LIMIT. The other 90 move on to aggregate functions, GROUP BY, HAVING, INNER JOIN, LEFT JOIN, CASE, subqueries, CTEs, and window functions. You unlock all of them with one in-app purchase. There's no subscription and nothing recurring. When you're stuck Each exercise has three hints, and you open them one at a time. The first gives you only the idea. If that's not enough, the second shows the shape of the query, and the third tells you which tables and columns to use. We set it up this way so you don't have to jump straight to the answer. There's also a sample solution with an explanation, and you can tap any underlined term in a problem to see what it means. Coming back to it Your drafts save automatically, so you can close the app halfway through a query and finish it later. Missed exercises and bookmarks are kept together so you can try them again. Anything you get wrong comes back the next day. Exercises you get right come back too, after 3 days, then a week, then 3 weeks. The editor suggests SQL keywords and column names as you type, and you can look at the tables and their data at any point. It works on iPhone and iPad, in light or dark mode. If you've gone through a course or a book and want to actually use what you learned, this is a good next step. It also works as a warm-up before a SQL test or a technical interview. Before you download • The practice data is set in Japan, so some names, places, and text values are in Japanese. A few exercises ask you to type Japanese text into your query, such as WHERE city = '東京'. The exercise shows you the exact text to use. • You can practice and check answers offline. You only need a connection to buy or restore the unlock. • There are no ads. Exercise 1 is a single line that pulls every customer's name. It's a good place to start.