$mod (aggregation)

Definition定义

$mod

Divides one number by another and returns the remainder.将一个数字除以另一个数字并返回余数。

The $mod expression has the following syntax:$mod表达式具有以下语法：

{ $mod: [ <expression1>, <expression2> ] }

The first argument is the dividend, and the second argument is the divisor; i.e. first argument is divided by the second argument.第一个自变量是被除数，第二个自变量是除数；第一个自变量除以第二个自变量。

The arguments can be any valid expression as long as they resolve to numbers. 参数可以是任何有效的表达式，只要它们解析为数字即可。For more information on expressions, see Expressions.有关表达式的详细信息，请参阅表达式。

Example实例

Consider a conferencePlanning collection with the following documents:考虑一个包含以下文档的conferencePlanning（会议计划）集合：

db.conferencePlanning.insertMany( [
   { "_id" : 1, "city" : "New York", "hours" : 80, "tasks" : 7 },
   { "_id" : 2, "city" : "Singapore", "hours" : 40, "tasks" : 4 }
] )

The following aggregation uses the $mod expression to return the remainder of the hours field divided by the tasks field:以下聚合使用$mod表达式返回hours字段除以tasks字段的余数部分：

db.conferencePlanning.aggregate(
   [
     { $project: { remainder: { $mod: [ "$hours", "$tasks" ] } } }
   ]
)

The operation returns the following results:该操作返回以下结果：

{ "_id" : 1, "remainder" : 3 }
{ "_id" : 2, "remainder" : 0 }