Database
[{"_id":ObjectId("6336d94e0330f5d48e44fb0f"),"systemId":"5124301","userId":"9876543210",/**"tempId": "123456da87sdafasdf",*/"updatedAt":ISODate("2022-09-30T12:01:11.714Z"),"receivedAt":ISODate("2022-04-10T23:15:08.145Z"),}]
Query
db.collection.update({systemId:"5124301"},[{$set:{userId:"1234567890",receivedAt:ISODate("2022-04-10T23:15:08.145Z"),tempId:{$ifNull:["$tempId","13qeqrwrqwtqrfsdfweqr"]}}}])