前言
1.$add操作符（+）
$add操作符的语法：
{ "_id" : 1, "item" : "abc", "price" : 10, "fee" : 2, date: ISODate("2014-03-01T08:00:00Z") } { "_id" : 2, "item" : "jkl", "price" : 20, "fee" : 1, date: ISODate("2014-03-01T09:00:00Z") } { "_id" : 3, "item" : "xyz", "price" : 5, "fee" : 0, date: ISODate("2014-03-15T09:00:00Z") } db.sales.aggregate( [ { $project: { item: 1, total: { $add: [ "$price", "$fee" ] } } } ] ) { "_id" : 2, "item" : "jkl", "total" : 21 } { "_id" : 3, "item" : "xyz", "total" : 5 }
有效日期 命名为 expire_date，则相应的SQL如下： db.sales.aggregate( [ { $project: { item: 1, expire_date: { $add: [ "$date", 3*24*60*60*1000 ] } } } ] ) { "_id" : 2, "item" : "jkl", "expire_date" : ISODate("2014-03-04T09:00:00Z") } { "_id" : 3, "item" : "xyz", "expire_date" : ISODate("2014-03-18T09:00:00Z") } 注：此案例中有关时间的这种运算，在SQL Server 数据库中是通过函数 DATEADD(）来实现的。 2.$subtract操作符（－）
$subtract操作符的语法
{ "_id" : 1, "item" : "abc", "price" : 10, "fee" : 2, "discount" : 5, "date" : ISODate("2014-03-01T08:00:00Z") } { "_id" : 2, "item" : "jkl", "price" : 20, "fee" : 1, "discount" : 2, "date" : ISODate("2014-03-01T09:00:00Z") } db.sales.aggregate( [ { $project: { item: 1, total: { $subtract: [ { $add: [ "$price", "$fee" ] }, "$discount" ] } } } ] ) { "_id" : 2, "item" : "jkl", "total" : 19 }
db.sales.aggregate( [ { $project: { item: 1, dateDifference: { $subtract: [ new Date(), "$date" ] } } } ] ) { "_id" : 2, "item" : "jkl", "dateDifference" : NumberLong("154743494624") } 注：此案例中关于时间的这种运算，在SQL Server 数据库中是通过函数 DATEDiff(）来实现的。
实现SQL的语句如下 db.sales.aggregate( [ { $project: { item: 1, dateDifference: { $subtract: [ "$date", 3 * 60 * 60 * 1000 ] } } } ] ) { "_id" : 2, "item" : "jkl", "dateDifference" : ISODate("2014-03-01T06:00:00Z") }
3.$multiply操作符（*）
{ "_id" : 1, "item" : "abc", "price" : 10, "quantity": 2, date: ISODate("2014-03-01T08:00:00Z") } { "_id" : 2, "item" : "jkl", "price" : 20, "quantity": 1, date: ISODate("2014-03-01T09:00:00Z") } { "_id" : 3, "item" : "xyz", "price" : 5, "quantity": 10, date: ISODate("2014-03-15T09:00:00Z") } db.sales.aggregate( [ { $project: { item: 1, total_price: { $multiply: [ "$price", "$quantity" ] } } } ] ) { "_id" : 2, "item" : "jkl", "total_price" : 20 } { "_id" : 3, "item" : "xyz", "total_price" : 50 } 4.$divide操作符（/）
{ "_id" : 1, "name" : "A", "hours" : 80, "resources" : 7 }, { "_id" : 2, "name" : "B", "hours" : 40, "resources" : 4 } db.planning.aggregate( [ { $project: { name: 1, workdays: { $divide: [ "$hours", 8 ] } } } ] ) { "_id" : 2, "name" : "B", "workdays" : 5 } 5 求余 运算（$mod） { "_id" : 2, "project" : "B", "hours" : 40, "tasks" : 4 } db.planning.aggregate( [ { $project: { remainder: { $mod: [ "$hours", "$tasks" ] } } } ] ) { "_id" : 2, "remainder" : 0 } 6.案例分析 { "_id" : 1, "sno" : 201501010001, "name" : "xiaoming", "attendanceAvg" : 90, "quizzAvg" : 95, "testAvg" : 98, "teacherPet" : true } { "_id" : 2, "sno" : 201501010002, "name" : "xiaoli", "attendanceAvg" : 100, "quizzAvg" : 90, "testAvg" : 90, "teacherPet" : false } { "_id" : 3, "sno" : 201501010003, "name" : "xiaohong", "attendanceAvg" : 100, "quizzAvg" : 80, "testAvg" : 100, "teacherPet" : false } db.students.aggregate( [ { $project: { "sno": 1, "name": 1, grade: { $cond: ["$teacherPet", 100, { "$add": [ { "$multiply": ["$attendanceAvg", .1] }, { "$multiply": ["$quizzAvg", .3] }, { "$multiply": ["$testAvg", .6] } ] }] } } } ] ) { "_id" : 2, "sno" : 201501010002, "name" : "xiaoli", "grade" : 91 } { "_id" : 3, "sno" : 201501010003, "name" : "xiaohong", "grade" : 94 }
6.2 常用逻辑表达式 类别布尔表达式 {$and: [ , , ... ]} 控制表达式 或者 { $cond: [ , , ] } 犎绻鹐xpression是null，那就返回replacement-expression-if-null，否则返回expression。比较表达式 爗?strcasecmp:燵 , 燷爙
通过这些操作符，就可以在聚合中使用更复杂的逻辑。 总结
以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对自学php网的支持。
查看更多关于MongoDB中的加减乘除运算详解的详细内容...