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docs/db_design.md

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+# 🧾 3. Table Design (Detailed)
+
+---
+
+## `loan_applications` (MAIN TABLE)
+This is the core record.
+
+```sql
+id (PK)
+loan_type_id (FK)
+amount_requested
+deduction_period
+purpose
+
+status (SUBMITTED, UNDER_REVIEW, APPROVED, REJECTED)
+created_at
+updated_at
+```
+
+## `applicants`
+One-to-one with loan application.
+
+```sql
+id (PK)
+loan_application_id (FK)
+
+name
+ic_num
+phone_num
+member_id_num
+birth_date
+email
+
+employer_name
+current_position
+position_status
+
+address
+
+bank_account_number
+bank_name
+
+basic_salary
+total_income
+deduction
+
+service_date
+service_period
+```
+
+## `guarantors`
+👉 One loan → **3 guarantors** (One-to-Many)
+
+```sql
+id (PK)
+loan_application_id (FK)
+
+name
+ic_num
+unit
+address
+phone_num
+member_id_number
+
+basic_salary
+allowance
+total_income
+```
+
+## `loan_approvals`
+One-to-one with loan application.
+
+```sql
+id (PK)
+loan_application_id (FK)
+
+level
+role
+approver_id
+
+decision (PENDING, APPROVED, REJECTED)
+remarks
+
+approved_at
+```
+
+## `loan_evaluations`
+```sql
+id (PK)
+loan_application_id (FK)
+
+calculated_by (FK users)
+
+total_loan
+total_payment
+period
+
+insurance_per_month
+
+deduction_start_date
+deduction_end_date
+
+number_of_shares
+total_fees
+debt_balance
+
+payment_date
+
+created_at
+```
+
+## `documents`
+```sql
+id
+loan_application_id (FK)
+
+file_name
+file_url
+file_type
+
+uploaded_by
+uploaded_at
+```
+
+## `loan_status_history`
+```sql
+id (PK)
+loan_application_id (FK)
+
+status (DRAFT, SUBMITTED, UNDER_REVIEW, APPROVED, REJECTED)
+
+changed_by (FK users)
+changed_at (timestamp)
+
+remarks (optional)
+```
+
+## `repayments`
+```sql
+id (PK)
+loan_application_id (FK)
+
+installment_number (1, 2, 3...)
+
+due_date
+amount_due
+
+amount_paid
+payment_date
+
+status (PENDING, PAID, LATE)
+
+created_at
+```
+
+---
+
+# 🔗 4. Relationships Diagram (Simple)
+
+```id="c2x7qp"
+loan_applications
+    │
+    ├── applicants (1:1)
+    ├── guarantors (1:N)
+    └── loan_reviews (1:1)
+```
+
+---
+
+
+# 🧩 6. JPA Entity Mapping (Example)
+
+### LoanApplication
+
+```java
+@Entity
+public class LoanApplication {
+    @Id
+    @GeneratedValue
+    private Long id;
+
+    private BigDecimal amountRequested;
+    private Integer deductionPeriod;
+    private String purpose;
+
+    @Enumerated(EnumType.STRING)
+    private LoanStatus status;
+
+    @OneToOne(mappedBy = "loanApplication", cascade = CascadeType.ALL)
+    private Applicant applicant;
+
+    @OneToMany(mappedBy = "loanApplication", cascade = CascadeType.ALL)
+    private List<Guarantor> guarantors;
+
+    @OneToOne(mappedBy = "loanApplication", cascade = CascadeType.ALL)
+    private LoanReview review;
+}
+```
+
+---
+
+# ⚠️ 7. Important Constraints
+
+## 🔹 Enforce in Backend (NOT DB)
+
+* Exactly **3 guarantors**
+* Valid IC format
+* Salary > 0
+* Loan amount limits
+
+---
+
+# 🔐 8. Audit & Compliance (Very Important)
+
+Add these fields to key tables:
+
+```sql
+created_by
+created_at
+updated_by
+updated_at
+```
+
+---
+
+# 🚀 9. Future Enhancements
+
+You can easily extend this design with:
+
+* 📎 `documents` table (for uploads)
+* 📊 `repayments` table
+* 🧾 `audit_logs`
+* 🔄 `loan_status_history`
+
+---
+
+# 🏁 Final Architecture Mapping
+
+Your DB aligns perfectly with your system:
+
+```id="z7wq3f"
+Frontend Form → LoanApplication → Applicant + Guarantors
+                                      ↓
+                                Officer Review
+                                      ↓
+                                   Decision
+```
+