[英]How do I query for documents that have a blank list?
db.users.find({'friends':[]});
This doesn't work! 这行不通! I want documents that do not have anyone in "friends" attribute.
我想要在“朋友”属性中没有任何人的文档。
您可以使用$ size运算符轻松实现:
db.users.find({'friends': { $size: 0 }});
Try 尝试
db.users.find({'friends': {$size : 0}});
You can read about it here: 你可以在这里读到它:
http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24size http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24size
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