MongoDB 的使用总结使用多分支判断 switch...case...then

系统管理员 2023-02-08 12:47 13阅读 0赞

## mongodb 使用多分支判断 switch…case…then ##

mongodb switch多分支判断的结构如下

{
        
        "$switch": {
        
            "branches": [
                {
        
                    "case": {
        
                        "<判断条件>"
                    },
                    "then": ""
                },
                {
        
                    "case": {
        
                        "<判断条件>"
                    },
                    "then": ""
                },
                
            ],
            "default": "默认值"
        }
    }

mongodb switch多分支判断示例

// 构造测试数据
    db.col00.insertMany([
    	{
        "name": "doc01", "age": 10},
    	{
        "name": "doc02", "age": 11},
    	{
        "name": "doc03", "age": 12},
    	{
        "name": "doc03", "age": 20},
    	{
        "name": "doc04", "age": 21},
    	{
        "name": "doc05", "age": 22},
    	{
        "name": "doc07", "age": 30},
    	{
        "name": "doc08", "age": 31},
    	{
        "name": "doc09", "age": 32}
    ]);
    
    // 使用场景：针对测试数据，要实现对年龄（age）按区间进行分组聚合  
    // 注意点：$$ROOT表示文档自身
    db.col00.aggregate([
        {
        
            "$project": {
        
                "self": "$$ROOT",
                "ageKey": {
        
                    "$switch": {
        
                        "branches": [
                            {
        
                                "case": {
        
                                    "$lt": ["$age", 20]
                                },
                                "then": "0-20岁"
                            },
                            {
        
                                "case": {
        
                                    "$and": [{
        
                                        "$gte": ["$age", 20]
                                    }, {
        
                                        "$lt": ["$age", 30]
                                    }]
                                },
                                "then": "20-30岁"
                            }
                        ],
                        "default": "30岁以上"
                    }
                }
            }
        },
        {
        
            "$group": {
        
                "_id": "$ageKey",
                "count": {
        
                    "$sum": 1
                },
                "docs": {
        
                    "$push": "$self"
                }
            }
        }
    ])

mongodb switch多分支判断示例执行结果  
![示例执行结果][467e9769c51a4b2b9c7664e9bc34dce3.png]

[467e9769c51a4b2b9c7664e9bc34dce3.png]: /images/20230208/ccf07e5acc914900903aed6a543ebd50.png