以下哪项是有效的MongoDB文档？( )
{"user_name:"John"}
{}
{"user_name"="John"}
{"user_name":"John", category:["first":"IT", "second":"Networking"]}
青云测评
青云测评
以下哪项是有效的MongoDB文档？( )
{"user_name:"John"}
{}
{"user_name"="John"}
{"user_name":"John", category:["first":"IT", "second":"Networking"]}
