Query Operators

Introduction

MongoDB ships dozens of query operators that let you express anything SQL can — and more. They're grouped into comparison, logical, element, array, evaluation and geospatial categories.

Understanding the topic

• Comparison — $eq, $ne, $gt, $gte, $lt, $lte, $in, $nin.
• Logical — $and, $or, $not, $nor.
• Element — $exists, $type.
• Array — $all, $elemMatch, $size.
• Evaluation — $regex, $expr, $mod, $jsonSchema.

Syntax reference

db.users.find({
  age: { $gte: 18 },
  $or: [ { city: "NYC" }, { city: "LA" } ],
  tags: { $all: ["pro", "verified"] },
  email: { $regex: /@example\.com$/i }
});

Real-world use

Most application filters are 2-3 operators stacked — get fluent here.

Best practices

• Use $in instead of multiple $or branches.
• Prefer $elemMatch for multi-condition array filters.