Beginner LevelSQL & MySQL
How do SELECT, WHERE, ORDER BY, and LIMIT clauses filter relational datasets?
❓ Interview Prompt: Explain SQL query execution order, SELECT projection, WHERE filters, ORDER BY sorting, and LIMIT pagination.
Understanding the logical execution order of SQL queries is essential for writing efficient queries:
Logical Query Execution Order:
1
FROM & JOIN: Identifies target tables and joins rows.
2
WHERE: Filters rows based on boolean conditions before grouping.
3
GROUP BY: Aggregates rows sharing common column values.
4
HAVING: Filters aggregated groups.
5
SELECT: Projects specified columns and evaluates expressions.
6
ORDER BY: Sorts the final result set.
7
LIMIT / OFFSET: Restricts output row count.
Code Implementation Example
sql
SELECT id, first_name, email, created_at
FROM users
WHERE status = 'ACTIVE' AND age >= 21
ORDER BY created_at DESC
LIMIT 10 OFFSET 0;💡Filtering, sorting, and paginating query result sets.
🎯 Interview Key Takeaway
Remember that WHERE filters individual rows before grouping, while HAVING filters summary groups after aggregate computation.
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