Database & Query Performance rules

Do not perform multiple DB queries inside a loop for data you could fetch in one query. Instead, consolidate using IN clauses or JOINs to retrieve all needed data at once.

Extract reusable SQL fragments/builders for commonly repeated WHERE/ORDER clauses.

Use executemany/bulk operations and commit in sensible batches for large writes.

Use appropriate column types/lengths (e.g., NVARCHAR(128) vs NVARCHAR(MAX)) for fields with known bounds.

Deduplicate identical queries within a request; reuse previously fetched data or preload in a single query.

Set sensible timeouts for queries/transactions and avoid excessively long timeouts that mask problems.

Prefer set-based SQL (DELETE/UPDATE with WHERE IN/JOIN) or chunked batches over per-row statements.

Always specify ORDER BY when the processing logic relies on a particular order.