Sql server non unique clustered index關於「MongoDB unique」標籤，搜尋引擎有相關的訊息討論：
Unique Indexes — MongoDB Manualwww.mongodb.com › ... › Indexes › Index PropertiesQuery for Unique Documents in mongo DB collection - Stack Overflowstackoverflow.com › questions › query-for-unique-docum...Understanding `unique` in Mongoose - Mastering JSmasteringjs.io › tutorial