# GetItemTaxonomyAssignment

## Overview

GetItemTaxonomyAssignment retrieves a specific item-to-taxonomy-node assignment by the composite key of itemId and taxonomyNodeId. Used for duplicate detection during assignment creation and existence verification before removal.

## Business Rules

- Searches ItemTaxonomyAssignment table using both itemId AND taxonomyNodeId as a composite filter
- Returns the full assignment record if found (id, itemId, taxonomyNodeId, timestamps)
- Returns null if no assignment exists for the given pair

## Process Flow

```mermaid
flowchart TD
    A[Receive itemId + taxonomyNodeId] --> B[SELECT from ItemTaxonomyAssignment where itemId = input AND taxonomyNodeId = input]
    B --> C{Assignment found?}
    C -->|Yes| D[Return assignment record]
    C -->|No| E[Return null]
```

## External Dependencies

- None

## Error Scenarios

- **ASSIGNMENT_NOT_FOUND**: No assignment exists for the specified item and taxonomy node combination

## Test Cases

- returns assignment when found
- returns null when assignment not found