SQL
How a Query Executes and Reading EXPLAIN
What happens between typing a query and getting rows, and how to read an execution plan - the single most useful performance skill in SQL.
Query Performance
Execution plans, EXPLAIN, scans, seeks and query optimisation.
3 notes
Notes
SQL
Scans, Seeks, Join Strategies and Sorting
What the engine actually does: full scans versus index seeks, nested loop and hash joins, and why a sort or a temporary table appears in your plan.
SQL
Query Optimisation and Pagination Performance
A practical checklist for making a slow query fast, and the specific fix for deep pagination that no amount of indexing solves.