比较查询中的两个字段

Question

嗨，我有一个查询，我想比较两个字段，如果它们的值是S，则我有一个名为Sum的字段，我想在其中添加值1，如果字段的值不同或一个字段为null，则我想要总和字段显示为0

类似这样的东西：

{
  "name": "functions",
  "description": "Cloud Functions for Firebase",
  "scripts": {
    "serve": "firebase serve --only functions",
    "shell": "firebase functions:shell",
    "start": "npm run shell",
    "deploy": "firebase deploy --only functions",
    "logs": "firebase functions:log"
  },
  "engines": {
    "node": "8"
  },
  "dependencies": {
    "firebase-admin": "^8.6.0",
    "firebase-functions": "^3.3.0"
  },
  "devDependencies": {
    "firebase-functions-test": "^0.1.6"
  },
  "private": true

}