MongoDB查詢如何只輸出部分欄位內容

例如集合test,欄位有id,url和data三列，現在我們只想輸出id和url欄位，可以按如下方法來查:
> db.test.find( {}, { id: 1, url: 1 } )
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f39d"), "url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f39e"), "url" : "http://mp.weixin.qq.com/s?__biz=MzIwOTY0NjY5NA==&mid=2247487505&idx=3&sn=8bdfc5b35eaa5eb7d2dbc2ff6247bf06&chksm=9771f518a0067c0e982d834821f9a44b7eea39f60cff8d50886175bbe1c93b27c70a8af9bfd9&scene=0#rd" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f39f"), "url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a0"), "url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a1"), "url" : "http://mp.weixin.qq.com/s?__biz=MzU1NzE3MTEzOQ==&mid=2247486132&idx=7&sn=e031435df54cc5c6dcbdab4136c73222&chksm=fc38a218cb4f2b0e0b581ea5d7ef13f95d29321b385fe51137c8cd102b715ebfb75c284aacb0&scene=0#rd" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a2"), "url" : "http://mp.weixin.qq.com/s?__biz=MzAxOTMxMTAxOA==&mid=2650490009&idx=2&sn=020a9d674e4f48da10f3ed376bdda67f&chksm=83c7145cb4b09d4a153515ef56755098bccfbca92f7fb379621ffbe4177fc8431181a2d1f2cc&scene=0#rd" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a3"), "url" : "http://mp.weixin.qq.com/s?__biz=MzI0NTU3NDY1NQ==&mid=2247487947&idx=1&sn=0daadc7945dd56fa7f1c7c61557646ed&chksm=e94d2f5bde3aa64dc6578e1ce9997c5cbe57fc0500222dd9939da33877168afb3297045a50f8&scene=0#rd" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a4"), "url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a5"), "url" : "http://mp.weixin.qq.com/s?__biz=MzA5ODU0NzQ4OA==&mid=2649879715&idx=1&sn=5bdf0a2ca64b51df037252da73fe9d1c&chksm=888ab6ecbffd3ffa97bc454aef5e490eb8c4d5bd79e7dd61c833107dd907e3b7b6600bb7d111&scene=0#rd" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3a6"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3a7"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3a8"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3a9"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3aa"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3ab"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3ac"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3ad"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3ae"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3af"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3b0"), "url" : "" }
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備註:第一個引數為查詢條件，空代表查詢所有


//如果不想要某個欄位，可以用排除欄位的方法
例如排除data欄位的內容:
> db.test.find( {}, {data: 0 } )
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f39d"), "url" : "", "error" : "BSON document too large (25962119 bytes) - the connected server supports BSON document sizes up to 16793598 bytes." }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f39e"), "url" : "http://mp.weixin.qq.com/s?__biz=MzIwOTY0NjY5NA==&mid=2247487505&idx=3&sn=8bdfc5b35eaa5eb7d2dbc2ff6247bf06&chksm=9771f518a0067c0e982d834821f9a44b7eea39f60cff8d50886175bbe1c93b27c70a8af9bfd9&scene=0#rd", "web_url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f39f"), "url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a0"), "url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a1"), "url" : "http://mp.weixin.qq.com/s?__biz=MzU1NzE3MTEzOQ==&mid=2247486132&idx=7&sn=e031435df54cc5c6dcbdab4136c73222&chksm=fc38a218cb4f2b0e0b581ea5d7ef13f95d29321b385fe51137c8cd102b715ebfb75c284aacb0&scene=0#rd", "web_url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a2"), "url" : "http://mp.weixin.qq.com/s?__biz=MzAxOTMxMTAxOA==&mid=2650490009&idx=2&sn=020a9d674e4f48da10f3ed376bdda67f&chksm=83c7145cb4b09d4a153515ef56755098bccfbca92f7fb379621ffbe4177fc8431181a2d1f2cc&scene=0#rd", "web_url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a3"), "url" : "http://mp.weixin.qq.com/s?__biz=MzI0NTU3NDY1NQ==&mid=2247487947&idx=1&sn=0daadc7945dd56fa7f1c7c61557646ed&chksm=e94d2f5bde3aa64dc6578e1ce9997c5cbe57fc0500222dd9939da33877168afb3297045a50f8&scene=0#rd", "web_url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a4"), "url" : "" }
{ "_id" : ObjectId("5ad8a51bb5cec3000b17f3a5"), "url" : "http://mp.weixin.qq.com/s?__biz=MzA5ODU0NzQ4OA==&mid=2649879715&idx=1&sn=5bdf0a2ca64b51df037252da73fe9d1c&chksm=888ab6ecbffd3ffa97bc454aef5e490eb8c4d5bd79e7dd61c833107dd907e3b7b6600bb7d111&scene=0#rd", "web_url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3a6"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3a7"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3a8"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3a9"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3aa"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3ab"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3ac"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3ad"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3ae"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3af"), "url" : "" }
{ "_id" : ObjectId("5ad8a51cb5cec3000b17f3b0"), "url" : "" }
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