How do I query for documents that have a blank list?
Question
db.users.find({'friends':[]});
This doesn't work! I want documents that do not have anyone in "friends" attribute.
2 answers
solution1
0 2011-09-14 16:23:02
您可以使用$ size运算符轻松实现：
db.users.find({'friends': { $size: 0 }});
solution2
0 ACCPTED 2011-09-14 16:27:21
Try
db.users.find({'friends': {$size : 0}});
You can read about it here:
http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24size
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