Multiple filter parameters in Rest API - Step-by-Step Execution

Concept Flow - Multiple filter parameters

Client sends request with multiple filters

↓

Server receives request

↓

Parse each filter parameter

↓

Apply filters to data query

↓

Fetch filtered data

↓

Send filtered data back to client

The server receives a request with several filter parameters, parses them, applies all filters to the data query, then returns the filtered results.

Execution Sample

Rest API

GET /items?color=red&size=medium&in_stock=true

// Server parses filters
filters = {"color": "red", "size": "medium", "in_stock": true}

// Query database with filters
results = db.query(filters)

// Return results

This example shows a client requesting items filtered by color, size, and stock status, and the server processing these filters to return matching items.

Execution Table

Step	Action	Filter Parameters	Query Applied	Result
1	Receive request	color=red, size=medium, in_stock=true	null yet	Waiting to parse filters
2	Parse filters	color=red, size=medium, in_stock=true	null yet	Filters stored as dictionary
3	Apply filters to query	{"color": "red", "size": "medium", "in_stock": true}	SELECT * FROM items WHERE color='red' AND size='medium' AND in_stock=TRUE	Query ready
4	Execute query	{"color": "red", "size": "medium", "in_stock": true}	Same as above	Filtered items fetched
5	Send response	{"color": "red", "size": "medium", "in_stock": true}	N/A	Filtered items sent to client
6	End	N/A	N/A	Request complete

💡 All filters applied; data fetched and response sent to client

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
filters	null	{"color": "red", "size": "medium", "in_stock": true}	{"color": "red", "size": "medium", "in_stock": true}	{"color": "red", "size": "medium", "in_stock": true}
query	null	null	SELECT * FROM items WHERE color='red' AND size='medium' AND in_stock=TRUE	Same as after Step 3
results	null	null	null	List of filtered items

Key Moments - 3 Insights

Why do we parse filter parameters before applying them to the query?

Parsing converts the raw query string into a structured format (like a dictionary) so the server can correctly build the database query, as shown in Step 2 of the execution_table.

What happens if one filter parameter is missing?

The server applies only the filters provided. Missing filters mean those conditions are not included in the query, so more data may be returned. This is implied between Steps 2 and 3.

Why do we combine all filters with AND in the query?

Using AND ensures that only items matching all filter conditions are returned, as shown in the query in Step 3.

Visual Quiz - 3 Questions

Look at the execution_table at Step 3. What does the query include?

A Only the color filter

B All filters combined with AND

C Color and size filters combined with OR

D No filters applied

💡 Hint

Check the 'Query Applied' column at Step 3 in the execution_table

According to variable_tracker, what is the value of 'filters' after Step 2?

A null

B Empty dictionary {}

C {"color": "red", "size": "medium", "in_stock": true}

D List of items

💡 Hint

Look at the 'filters' row under 'After Step 2' in variable_tracker

If the client sends only 'color=blue' as a filter, how would the query change at Step 3?

A SELECT * FROM items WHERE color='blue'

B SELECT * FROM items WHERE size='medium'

C SELECT * FROM items WHERE color='red' AND size='medium'

D No query is made

💡 Hint

Filters in the query match exactly what is parsed from the request (see execution_table Step 3)

Concept Snapshot

Multiple filter parameters let clients narrow data by sending several conditions.
Server parses each filter, then combines them with AND in the query.
Filters are optional; missing ones are ignored.
This helps return only data matching all requested criteria.

Full Transcript

When a client sends a request with multiple filter parameters, the server first receives the request. It then parses the filter parameters into a structured format like a dictionary. Next, the server applies all these filters combined with AND to build a database query. The query fetches only the items matching all filters. Finally, the server sends the filtered data back to the client. This process ensures clients get exactly the data they want by specifying multiple conditions.