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skills/data-validation/examples/INDEX.md

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+# Data Validation Examples
+
+Complete examples for Pydantic v2 validation, database schema alignment, and data quality monitoring.
+
+## Examples Overview
+
+### User Validation Example
+**File**: [user-validation-example.md](user-validation-example.md)
+
+Complete user validation workflow with:
+- Pydantic v2 model with field validators
+- Email, username, age validation
+- Cross-field validation (admin age requirement)
+- SQLModel database alignment
+- FastAPI integration
+- Validation error formatting
+- Pytest test suite
+
+**Use when**: Building user registration, profile management, or authentication.
+
+---
+
+### Order Validation Example
+**File**: [order-validation-example.md](order-validation-example.md)
+
+Complex order validation with:
+- Nested object validation (order items, shipping address)
+- Currency and pricing validation
+- Inventory quantity checks
+- Multi-tenant validation (tenant_id)
+- Custom validators for business rules
+- Database transaction validation
+
+**Use when**: Building e-commerce, order management, or invoicing systems.
+
+---
+
+### Nested Validation Example
+**File**: [nested-validation.md](nested-validation.md)
+
+Advanced nested validation patterns:
+- Nested Pydantic models
+- List validation with min/max items
+- Discriminated unions for polymorphic data
+- Recursive validation (tree structures)
+- Forward references
+- Validation context passing
+
+**Use when**: Working with complex JSON structures, API payloads, or hierarchical data.
+
+---
+
+## Quick Reference
+
+| Example | Complexity | Key Patterns |
+|---------|-----------|--------------|
+| **User** | Basic | Field validators, cross-field validation |
+| **Order** | Intermediate | Nested objects, business rules, transactions |
+| **Nested** | Advanced | Discriminated unions, recursion, context |
+
+## Common Patterns
+
+### Basic Validation
+```python
+from pydantic import BaseModel, Field, EmailStr
+
+class User(BaseModel):
+    email: EmailStr
+    age: int = Field(ge=13, le=120)
+```
+
+### Field Validator
+```python
+from pydantic import field_validator
+
+class User(BaseModel):
+    username: str
+
+    @field_validator('username')
+    @classmethod
+    def validate_username(cls, v: str) -> str:
+        if len(v) < 3:
+            raise ValueError('Username too short')
+        return v
+```
+
+### Model Validator
+```python
+from pydantic import model_validator
+
+class User(BaseModel):
+    role: str
+    age: int
+
+    @model_validator(mode='after')
+    def check_admin_age(self):
+        if self.role == 'admin' and self.age < 18:
+            raise ValueError('Admins must be 18+')
+        return self
+```
+
+---
+
+Return to [main agent](../data-validator.md)