Lab: Build & Load stg_orders

# Lab: Build & Load stg_orders (Graded) ## Brief Create the staging table, load it from a SELECT, correct it, and prove the load is replay-safe. Work in your Postgres sandbox. ## Tasks 1. **CREATE** `stg_orders` with: `BIGINT` PK, `NOT NULL` customer + timestamp, non-negative `CHECK` on amount, `IF NOT EXISTS`. 2. **INSERT..SELECT** 2,000 rows from the provided `raw_orders_extract` seed (fixture attached) with an explicit column list. 3. **UPDATE** the miscoded `status='tset'` rows to `'test'` using SELECT-first discipline (paste both statements). 4. **Replay proof:** run your INSERT a second time with `ON CONFLICT DO NOTHING` and show row count unchanged (`SELECT COUNT(*)` before/after). 5. **ALTER**: add nullable `coupon_code TEXT` with `IF NOT EXISTS`. ## Acceptance (deterministic checks before review) - `stg_orders` exists with PK + CHECK intact. - Row count == seed count after replay (no duplicates). - `coupon_code` column present, all NULL. - Both SELECT-first statements pasted alongside each write. ## Starter Fixture `raw_orders_extract.csv` + skeleton `.sql` with TODO markers are attached.