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🧩 MongoDB: Conditional Operators

MongoDB conditional operators allow you to apply logic similar to if-else statements within the aggregation pipeline. These operators let you handle conditional calculations, replace null values, or perform multi-case branching.

📚 Sample Data Setup — employees Collection

Example01
MongoDB Shell
NoSQL
Database
1db.employees.insertMany([
2  { _id: 1, name: "Alice", salary: 50000, bonus: 2000, department: "Engineering" },
3  { _id: 2, name: "Bob",   salary: 45000, bonus: null, department: "Marketing" },
4  { _id: 3, name: "Cara",  salary: 60000, bonus: 5000, department: null }
5]);
Query Result
JSON Output
✅ 3 employee documents inserted successfully.

1️⃣ Using $cond — Ternary If-Then-Else

Example02
MongoDB Shell
NoSQL
Database
1db.employees.aggregate([
2  {
3    $project: {
4      name: 1,
5      adjustedBonus: {
6        $cond: {
7          if: { $gt: ["$salary", 50000] },
8          then: { $multiply: ["$bonus", 1.5] },
9          else: "$bonus"
10        }
11      }
12    }
13  }
14]);
Query Result
JSON Output
[
  { "_id": 1, "name": "Alice", "adjustedBonus": 2000 },
  { "_id": 2, "name": "Bob",   "adjustedBonus": null },
  { "_id": 3, "name": "Cara",  "adjustedBonus": 7500 }
]

2️⃣ Using $ifNull — Replace Null Values

Example03
MongoDB Shell
NoSQL
Database
1db.employees.aggregate([
2  {
3    $project: {
4      name: 1,
5      safeBonus: { $ifNull: ["$bonus", 0] },
6      safeDepartment: { $ifNull: ["$department", "Unassigned"] }
7    }
8  }
9]);
Query Result
JSON Output
[
  { "_id": 1, "name": "Alice", "safeBonus": 2000,  "safeDepartment": "Engineering" },
  { "_id": 2, "name": "Bob",   "safeBonus": 0,    "safeDepartment": "Marketing" },
  { "_id": 3, "name": "Cara",  "safeBonus": 5000, "safeDepartment": "Unassigned" }
]

3️⃣ Using $switch — Multi-Case Conditional

Example04
MongoDB Shell
NoSQL
Database
1db.employees.aggregate([
2  {
3    $project: {
4      name: 1,
5      salaryTier: {
6        $switch: {
7          branches: [
8            { case: { $lt: ["$salary", 45000] }, then: "Entry" },
9            { case: { $lt: ["$salary", 55000] }, then: "Mid" },
10            { case: { $gte: ["$salary", 55000] }, then: "Senior" }
11          ],
12          default: "Unknown"
13        }
14      }
15    }
16  }
17]);
Query Result
JSON Output
[
  { "_id": 1, "name": "Alice", "salaryTier": "Mid" },
  { "_id": 2, "name": "Bob",   "salaryTier": "Mid" },
  { "_id": 3, "name": "Cara",  "salaryTier": "Senior" }
]