Must-Know for Beginners: Basic MongoDB Query Syntax

This article introduces the basics of MongoDB querying. Core concepts include: collections (similar to tables) and documents (key-value pairs with a JSON structure). Basic preparations involve connecting to the MongoDB Shell, switching to the target database (e.g., "test"), and inserting a sample "users" collection with fields "name", "age", and "hobbies". Query methods covered are: `find()` to return all documents (with `pretty()` for formatting); conditional queries using key-value conditions, supporting comparison operators ($eq, $gt, $lt, etc.), logical operators ($and (default), $or, $not), regular expression matching for strings, and array operators ($in, $size). Advanced techniques include projection (specifying returned fields), sorting (using `sort()`), limiting results (`limit()`/`skip()`), statistics (`countDocuments()`), and deduplication (`distinct()`). Performance optimization tips are emphasized to avoid full collection scans. By practicing with combined conditions and result processing, users can quickly master MongoDB query logic.