如何在MongoDB中更新嵌套字段且不丢失原有数据？

Hey there! I totally get where you're stuck—your current update is replacing the entire keys subdocument because you're passing a new object directly to $set for that field. Instead, we need to target the specific new field inside keys without touching the existing data.

Correct Update Command #

Use dot notation to specify the new subfield you want to add, and MongoDB will preserve the rest of the keys content:

db.collection_name.update(
  {"_id": 1},
  {$set: {"keys.updatedTes": "string"}}
)

Why This Works #

• The filter {"_id": 1} still correctly targets your document.
• By writing {"keys.updatedTes": "string"}, you're telling MongoDB to only add (or update, if it already exists) the updatedTes field within the keys subdocument. Your original login_id and transaction_key values will stay right where they are.

Bonus: Add Multiple Fields at Once #

If you ever need to add or update several fields in keys later, you can extend the $set like this—no overwriting happens here either:

db.collection_name.update(
  {"_id": 1},
  {$set: {
    "keys.updatedTes": "string",
    "keys.another_field": "new_value"
  }}
)

内容的提问来源于stack exchange，提问作者catter