What experience do you have with SQL? JOIN, window functions, aggregate functions? Do you write the queries yourself or through developers?

I have experience writing SQL queries, including the use of JOIN, window, and aggregate functions.

• I use JOIN to combine data from multiple tables, for example, INNER JOIN for related records.

• I use window functions to calculate moving sums, rankings, or aggregates by groups without grouping the entire dataset.

• I apply aggregate functions (SUM, COUNT, AVG, MAX, MIN) for summary data.

Example of a query using JOIN and window function:

SELECT
  user_id,
  order_date,
  SUM(amount) OVER (PARTITION BY user_id ORDER BY order_date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS running_total
FROM orders
WHERE order_date >= '2024-01-01';

I usually write queries independently for data analysis and verification, but for complex optimized queries, I can collaborate with developers or DBAs.