Multiple Queries

Learn the fundamentals of multiple queries in FastAPI.

🎯 Core Concept

Multiple query parameters allow you to filter, sort, and paginate data. Most real-world APIs use multiple query parameters for flexible data retrieval.

📖 What You'll Learn

In this section, you'll understand:

• Combining multiple query parameters

• How it applies to real-world API development

• Designing flexible query interfaces

• Common patterns and best practices

💡 Basic Multiple Queries

from fastapi import FastAPI
from typing import Optional

app = FastAPI()

@app.get("/items")
async def list_items(
    skip: int = 0,
    limit: int = 10,
    category: Optional[str] = None,
    active: bool = True
):
    # Multiple query parameters
    # GET /items → skip=0, limit=10, category=None, active=True
    # GET /items?skip=10&limit=20 → skip=10, limit=20, category=None, active=True
    # GET /items?category=electronics&active=false → skip=0, limit=10, category="electronics", active=False
    return {
        "skip": skip,
        "limit": limit,
        "category": category,
        "active": active
    }

🔍 Complex Query Scenarios

# Product search with filters
@app.get("/products")
async def search_products(
    q: str,                      # Required search term
    category: Optional[str] = None,
    min_price: Optional[float] = None,
    max_price: Optional[float] = None,
    in_stock: bool = True,
    sort: str = "relevance",
    page: int = 1,
    per_page: int = 20
):
    # Build dynamic query based on filters
    filters = {"q": q, "in_stock": in_stock}
    if category:
        filters["category"] = category
    if min_price:
        filters["min_price"] = min_price
    if max_price:
        filters["max_price"] = max_price

    # Search products
    results = db.search_products(**filters)
    results = sort_results(results, sort)

    # Paginate
    skip = (page - 1) * per_page
    paginated = results[skip:skip + per_page]

    return {
        "total": len(results),
        "page": page,
        "per_page": per_page,
        "products": paginated
    }

How it applies to real-world API development

Multiple query parameters are essential for:

• **E-commerce**: Filter by category, price range, ratings

• **Search engines**: Query, filters, sorting, pagination

• **Analytics**: Date range, metrics, grouping, limits

• **Content management**: Status, author, date range, types

🔑 Key Takeaways

• ✅ Understand the purpose of multiple queries

• ✅ Know when to apply this pattern

• ✅ Recognize its benefits in real-world scenarios

• ✅ Be prepared to use it in your projects

Ready to explore more? Check out the advanced section for production patterns and edge cases.