ETL pipelines move data between systems, for example from accounting exports and spreadsheets into a reporting database. The transform step standardizes formats, applies business rules, removes duplicates, and validates values.
Reliable pipelines are repeatable, logged, and checked. Each run should reconcile counts and totals with the source, flag records that fail validation, and keep raw data so problems can be traced. A variant, ELT, loads raw data first and transforms it inside the target database.