Features
The initial static version includes searchable SQL practice problems and detailed problem views. The structure is ready for interview questions, DBMS notes, an error dictionary, and cheatsheets.
SQLHub provides practical query problems that ask learners to write SQL against a clear table schema. Problems are organized by category, difficulty, tags, and DBMS so learners can focus on the concepts they need most.
The current set covers SELECT, WHERE, ORDER BY, GROUP BY, JOIN, subqueries, aggregate functions, NULL handling, set operators, and window functions.
Problem details can be opened with crawlable URLs such as problems/find-users-older-than-20.html. Each detail view includes the problem, schema, sample data, expected output, hidden answer, explanation, common mistakes, and related concepts.
This makes each problem more useful than a simple question card.
Explanations describe what the query does and why each important clause is needed. Beginners can compare the answer to the sample output and understand how the database produces the result.
Future pages can expand explanations with clause-by-clause walkthroughs.
SQL learners often make small mistakes that change the result completely. SQLHub highlights issues such as using = NULL instead of IS NULL, using WHERE for aggregate filters, or selecting extra columns with GROUP BY.
This section helps learners debug their own thinking.
Problems use Beginner, Intermediate, and Advanced labels so learners can choose an appropriate challenge. Difficulty levels also help future category pages guide visitors through a progressive learning path.
This is useful for both self-study and interview preparation.
Tags connect problems to specific concepts such as comparison operators, aliases, scalar subqueries, HAVING, and aggregate functions. Categories make browsing easier and create a clean foundation for SEO-friendly topic pages.
As the problem library grows, tags will help users find related practice quickly.
Many SQL concepts are shared across databases, but real projects often depend on DBMS-specific behavior. SQLHub is prepared to add notes about MySQL and PostgreSQL differences, including syntax, date handling, LIMIT patterns, and common error messages.
These notes can appear alongside relevant problems.
Interview-focused pages can explain common topics such as INNER JOIN vs LEFT JOIN, GROUP BY rules, indexes, transactions, normalization, and query optimization basics. The tone will stay practical and beginner-friendly.
This content can support developers preparing for junior and data-oriented roles.
An SQL error dictionary can target real search needs such as MySQL Error 1064, PostgreSQL column does not exist, and common GROUP BY errors. Each page can explain the cause, show a broken query, provide a corrected query, and list prevention tips.
This creates useful content beyond practice questions.
Cheatsheets can summarize frequently used SQL clauses, aggregate functions, joins, NULL handling, and date functions. They should be concise but linked to deeper practice pages so learners can move from reference material to hands-on query work.
This will support quick review before interviews and exams.