# Database Guidelines (Access, SQLite, SQL Server, Postgres)

1. **MS Access (.mdb / .accdb):**
   - Use correct date literals (`#YYYY-MM-DD#`).
   - Escape field names with square brackets (e.g., `[Order Date]`).
   - Be cautious with concurrent write operations and file locking.
2. **Cross-Engine Dialect Awareness:**
   - Access: `TOP n`, `IIF()`, string concatenation with `&`
   - SQLite: `LIMIT n`, `IFNULL()`, string concatenation with `||`
   - SQL Server: `TOP (n)`, `ISNULL()`, `CONCAT()`
   - Postgres: `LIMIT n`, `COALESCE()`, `||`, boolean literals (`TRUE`/`FALSE`)
3. **Parameterization:** Always use parameterized queries regardless of engine.
4. **Migrations:** Every schema change must include a rollback/backward-compatibility note in the spec.