Maria Garcia

Window functions perform calculations across row sets without grouping. ROWNUMBER assigns unique sequential numbers. RANK/DENSERANK handle ties differently. I use PARTITION BY to reset calculations per group. ORDER BY determines calculation order with

Indexes dramatically speed up queries but slow down writes. B-tree indexes handle equality and range queries—default for most databases. I create indexes on foreign keys, frequently queried columns, and WHERE/ORDER BY clauses. Composite indexes order

SQL joins combine data from multiple tables. INNER JOIN returns matching rows only. LEFT/RIGHT JOIN includes all rows from one table, nulls for non-matches. FULL OUTER JOIN combines both. I use CROSS JOIN for Cartesian products sparingly—performance k