Build DiD dataset with SQL

You need to build analysis panels for a staggered-adoption Difference-in-Differences (DiD) study that measures how a newly introduced shuttle service changes employee participation. A subset of sites launched the shuttle on a known date; the remaining sites never launched it. Write SQL that executes on a modern warehouse, such as BigQuery or PostgreSQL. Part A — employee-day panel. Return one row for every pairing of an employee with a panel date that is on or after that…