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iteye_15461

于 2013-11-09 22:05:59 发布

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分类专栏： mongodb

本文链接：https://blog.youkuaiyun.com/iteye_15461/article/details/82548421

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{
    "_id" : ObjectId("515d8f53175b8ecb053425c2"),
    "category" : "Batteries",
    "products" : [
        {
            "brand" : "Duracell",
            "item" : [
                "AA",
                "AAA"
            ]
        },
        {
            "brand" : "Everyday",
            "item" : [
                "9V",
                "AA",
                "12V"
            ]
        }
    ]
}

{["AA", "AAA", "9V", "12V"]} 和 
{
    "category" : "Batteries",
    "item": ["AA", "AAA", "9V", "12V"]
}

db.xyz.aggregate( {$project: {a: '$products.item'}}, 
    {$unwind: '$a'}, 
    {$unwind: '$a'}, 
    {$group: {_id: 'a', items: {$addToSet: '$a'}}});
db.xyz.aggregate( {$project: {category: 1, a: '$products.item'}}, 
    {$unwind: '$a'}, 
    {$unwind: '$a'}, 
    {$group: {_id: '$category', items: {$addToSet: '$a'}}});