MongoDB查詢內嵌文檔

標籤：mongodb   查詢內嵌文檔   

有文檔如下：

/* 0 */{  "_id" : ObjectId("55d09915331c571b60035d95"),  "title" : "hello world",  "comment" : [{      "author" : "joe",      "score" : 3    }, {      "author" : "tom",      "score" : 5    }, {      "author" : "jean",      "score" : 9    }]}/* 1 */{  "_id" : ObjectId("55d0996a331c571b60035d96"),  "title" : "zhangsan",  "comment" : [{      "author" : "joe",      "score" : 7    }, {      "author" : "suam",      "score" : 2    }, {      "author" : "jean",      "score" : 3    }]}/* 2 */{  "_id" : ObjectId("55d099b1331c571b60035d97"),  "title" : "lisi",  "comment" : [{      "author" : "wangwu",      "score" : 4    }, {      "author" : "suam",      "score" : 8    }, {      "author" : "tom",      "score" : 6    }]}

請問如何查詢author為joe，並且score為5以上的評論。

正確答案為

db.test.find({ "comment" : { "$elemMatch" : { "author" : "joe", "score" : { "$gte" : 5 } } } })

如果直接是

db.test.find({ "comment" : { "author" : "joe", "score" : { "$gte" : 5 } } })

來查詢，那麼內嵌文檔的匹配必須要整個文檔完全符合。

如果使用

db.test.find({ "comment.author" : "joe", "comment.score" : { "$gt" : 5 } })

那麼符合auhor條件和符合score條件的評論可能不是同一條，也就是說會查詢出以下兩條文檔

/* 0 */{  "_id" : ObjectId("55d09915331c571b60035d95"),  "title" : "hello world",  "comment" : [{      "author" : "joe",      "score" : 3    }, {      "author" : "tom",      "score" : 5    }, {      "author" : "jean",      "score" : 9    }]}/* 1 */{  "_id" : ObjectId("55d0996a331c571b60035d96"),  "title" : "zhangsan",  "comment" : [{      "author" : "joe",      "score" : 7    }, {      "author" : "suam",      "score" : 2    }, {      "author" : "jean",      "score" : 3    }]}

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MongoDB查詢內嵌文檔