【MongoDB学习笔记17】MongoDB的查询：find中的数组查询
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db.post.find()
{ "_id" : ObjectId("54a530c3ff0df3732bac1681"), "id" : 2, "name" : "joe", "age" : 30, "sex" : 1, "school" : "marry" }
{ "_id" : ObjectId("54a530c3ff0df3732bac1680"), "id" : 1, "name" : "joe", "age" : 30, "comments" : [ "test2", "test9", "test5" ], "sex" : 1, "school" : "marry" }
{ "_id" : ObjectId("54a9700e1b5afd45354fd086"), "id" : 3, "test3" : 3 }
{ "_id" : ObjectId("54a9701c1b5afd45354fd087"), "id" : 4, "test4" : 4 }
{ "_id" : ObjectId("54a970281b5afd45354fd088"), "id" : 5, "test5" : 5 }
{ "_id" : ObjectId("54a970351b5afd45354fd089"), "id" : 6, "test6" : 6 }
{ "_id" : ObjectId("54a970781b5afd45354fd08a"), "id" : 7, "test7" : 7 }
{ "_id" : ObjectId("54a970831b5afd45354fd08b"), "id" : 8, "test8" : 8 }
{ "_id" : ObjectId("54a970901b5afd45354fd08c"), "id" : 9, "test9" : 9 }
{ "_id" : ObjectId("54a9709c1b5afd45354fd08d"), "id" : 10, "test10" : 10 }
{ "_id" : ObjectId("54aa8a90652d8bdfa0566d34"), "id" : 11, "test10" : 11 }
{ "_id" : ObjectId("54aa97b894dcf31069b590ca"), "id" : 12, "fruit" : [ "apple", "banana", "peach" ] }
{ "_id" : ObjectId("54aa97d794dcf31069b590cb"), "id" : 13, "fruit" : [ "apple", "kumquat", "orange" ] }
{ "_id" : ObjectId("54aa97f294dcf31069b590cc"), "id" : 14, "fruit" : [ "cherry", "banana", "apple" ] }
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一、$all来匹配数组中的一组元素
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> db.post.find({"fruit":{$all:["apple","banana"]}})
{ "_id" : ObjectId("54aa97b894dcf31069b590ca"), "id" : 12, "fruit" : [ "apple", "banana", "peach" ] }
{ "_id" : ObjectId("54aa97f294dcf31069b590cc"), "id" : 14, "fruit" : [ "cherry", "banana", "apple" ] }
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可以看到apple和banana的顺序无关系；
二、$size来查询匹配的数组长度；
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> db.post.find({},{"id":1,"fruit":1,"_id":0})
{ "id" : 2 }
{ "id" : 1 }
{ "id" : 3 }
{ "id" : 4 }
{ "id" : 5 }
{ "id" : 6 }
{ "id" : 7 }
{ "id" : 8 }
{ "id" : 9 }
{ "id" : 10 }
{ "id" : 11 }
{ "id" : 12, "fruit" : [ "apple", "banana", "peach" ] }
{ "id" : 13, "fruit" : [ "apple", "kumquat", "orange", "fruit01" ] }
{}
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> db.post.find({"fruit":{$size:3}})
{ "_id" : ObjectId("54aa97b894dcf31069b590ca"), "id" : 12, "fruit" : [ "apple", "banana", "peach" ] }
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三、$slice操作符
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> db.post.find({"id":13})
{ "_id" : ObjectId("54aa97d794dcf31069b590cb"), "id" : 13, "fruit" : [ "apple", "kumquat", "orange", "fruit01" ] }
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返回数组前两个值
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> db.post.find({"id":13},{"fruit":{$slice:2}})
{ "_id" : ObjectId("54aa97d794dcf31069b590cb"), "id" : 13, "fruit" : [ "apple", "kumquat" ] }
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返回数组的后两个值
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> db.post.find({"id":13},{"fruit":{$slice:-2}})
{ "_id" : ObjectId("54aa97d794dcf31069b590cb"), "id" : 13, "fruit" : [ "orange", "fruit01" ] }
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返回数组中间的两个值
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> db.post.find({"id":13},{"fruit":{$slice:}})
{ "_id" : ObjectId("54aa97d794dcf31069b590cb"), "id" : 13, "fruit" : [ "kumquat", "orange" ] }
四、利用数组下表查询
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> db.post.find({"fruit.3":"fruit01"})
{ "_id" :
ObjectId("54aa97d794dcf31069b590cb"), "id" : 13, "fruit" : [ "apple", "kumquat",
"orange", "fruit01" ] }
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