Lab: Build & Load stg_orders

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.