What do you call complex SQL queries? Have you had to analyze them and with what tools?

Complex SQL queries are queries that include:

• Multiple JOINs between tables
• Nested subqueries
• Use of window functions
• GROUP BY with HAVING and aggregate functions
• Recursive queries
• Complex filtering and sorting conditions

Such queries are often used to obtain aggregated data, analytics, or to build complex samples.

When analyzing complex queries, I use the following tools:

• EXPLAIN and EXPLAIN ANALYZE to understand the execution plan and identify bottlenecks
• DBMS profilers (e.g., pgAdmin for PostgreSQL, SQL Server Management Studio for MS SQL)
• Slow query logging
• Visualization tools for execution plans

Example of using EXPLAIN:

EXPLAIN ANALYZE
SELECT u.id, u.name, COUNT(o.id) AS orders_count
FROM users u
LEFT JOIN orders o ON u.id = o.user_id
WHERE u.status = 'active'
GROUP BY u.id, u.name
HAVING COUNT(o.id) > 5
ORDER BY orders_count DESC;

This helps to understand which operations take the most time and to optimize queries, for example, by adding indexes or rewriting logic.