Advanced Queries

yourdb supports more complex queries beyond simple equality checks using MongoDB-style operators within the filter_dict. This allows you to filter based on ranges, inequalities, and multiple conditions.

Query Operators

The following operators can be used inside a nested dictionary as the value in your filter_dict:

• $gt: Greater than
• $lt: Less than
• $gte: Greater than or equal to
• $lte: Less than or equal to
• $ne: Not equal to
• $eq: Equal to (this is the default if no operator is specified)

Setup

We'll continue with the Product example from the Basic CRUD tutorial. Assume the database contains these items:

# Assumed data in the 'products' entity:
# Product(id=101, name='Laptop Pro', price=$1500, cat='Electronics')
# Product(id=103, name='Standing Desk', price=$500, cat='Furniture') # Price updated earlier
# Product(id=104, name='Monitor', price=$300, cat='Electronics') # Added for more examples
# Product(id=105, name='Office Chair', price=$250, cat='Furniture') # Added for more examples

Make sure the price field is included in the schema's indexes list for optimal performance on range queries (though the current implementation might still scan; see Core Concepts > Architecture).

    # Ensure 'price' is indexed in your schema definition
product_schema = {
    # ... other fields ...
    'price': "int",
    'category': "str",
    'indexes': ['category', 'price'] # <-- 'price' added
}

Examples

Range Queries ($gt, $lte)

Find products within a specific price range.

from yourdb import YourDB

db = YourDB("inventory_db") # Connect to the existing DB

# Find products costing more than $400
print("--- Products > $400 ---")
expensive_items = db.select_from("products", {'price': {'$gt': 400}})
for item in expensive_items:
    print(item)
# Expected: Laptop Pro ($1500), Standing Desk ($500)

# Find products costing $300 or less
print("\n--- Products <= $300 ---")
affordable_items = db.select_from("products", {'price': {'$lte': 300}})
for item in affordable_items:
    print(item)
# Expected: Monitor ($300), Office Chair ($250)

---

Inequality Query ($ne)

Find products that are not in a specific category.

# Find products that are NOT 'Electronics'
print("\n--- Non-Electronics Products ---")
others = db.select_from("products", {'category': {'$ne': 'Electronics'}})
for item in others:
    print(item)
# Expected: Standing Desk (Furniture), Office Chair (Furniture)

---

Combining Operators on the Same Field

Find products within a specific price band.

# Find products between $300 and $600 (inclusive)
print("\n--- Products between $300 and $600 ---")
mid_range = db.select_from("products", {
    'price': {'$gte': 300, '$lte': 600}
})
for item in mid_range:
    print(item)
# Expected: Standing Desk ($500), Monitor ($300)

Combining Multiple Fields

Find products matching criteria across different attributes. yourdb currently uses AND logic – all conditions in the filter_dict must be met.

# Find Furniture that costs less than $300
print("\n--- Furniture < $300 ---")
cheap_furniture = db.select_from("products", {
    'category': 'Furniture', # Equality check (uses index if available)
    'price': {'$lt': 300}    # Range check
})
for item in cheap_furniture:
    print(item)
# Expected: Office Chair ($250)

# Find Electronics that do NOT cost $1500
print("\n--- Electronics not costing $1500 ---")
other_electronics = db.select_from("products", {
    'category': 'Electronics',
    'price': {'$ne': 1500}
})
for item in other_electronics:
    print(item)
# Expected: Monitor ($300)