上一篇文章我们说到用 $where,但是这个办法有个严重的弊端: 性能消耗太多,一般是禁止这样进行使用script的,查询起来很慢.

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1.需要查询的表格

{	"health" : {			"diastolicpressure" : 95,			"systolicpressure" : 155,			"waist" : 72,	},	"calculation" : {			"target" : {				"systolicpressure" : 138,				"diastolicpressure" : 80,				"weight" : 67.375			},		}}{	"health" : {			"diastolicpressure" : 79,			"systolicpressure" : 120,			"waist" : 50,	},	"calculation" : {			"target" : {				"systolicpressure" : 138,				"diastolicpressure" : 80,				"weight" : 67.375			},		}}复制代码

2.需要查询的需求:

找出表格中health.diastolicpressure > calculation.target.diastolicpressure的数据

3单个条件比较查询实现 在shell中

db.members.aggregate(    [{            $match: {                sid: "aaa-PJx"   //筛选--先匹配这个,满足这个的才进行下面的匹配            }        },        {            $redact: {                "$cond": [{                        "$gt": ["$health.systolicpressure", "$calculation.target.systolicpressure"]                    },                    , "$$KEEP", "$$PRUNE"                ]            }        }    ]).pretty()复制代码

4.多个条件比较查询实现 在shell中

db.members.aggregate(    [        {            $match: {                sid: "aaa-PJx",            }        },        {            $redact: {                "$cond": [                    {                        "$and": [                            {                                "$gt": ["$health.systolicpressure", "$calculation.target.systolicpressure"]                                                    },                            {                                "$gt": ["$health.diastolicpressure", "$calculation.target.diastolicpressure"]                            }                        ]                    },                    "$$KEEP", "$$PRUNE"                ]            }        }    ]).pretty()复制代码