Play Modules Morphia 1.2.9a 之 Aggregation and Group aggregation

时间：2022-06-04 07:46:21

聚合 和 分组聚合：

PlayMorphia 它提供了基于开发人员models的友好接口

设想你定义了一个model。class Sales:

@Entity public class Sales extends Model {

    public String employeeId;

    public String department;

    public String region;

    public int amount;

}

聚合：如今你能够在Sales模型上做聚合操作，以下是一些详细演示样例： 

long total = Sales.count(); // also Sales.q().count();

long cntIT = Sales.q().filter("department", "IT").count();

long cntAU = Sales.q().filter("region", "AU").count();

long cntAuIt = Sales.find("region, department", "AU", "IT").count();

求和： 

long sum = Sales._sum("amount"); // also Sales.q().sum("amount");

long sumIT = Sales.find("department", "IT").sum("amount");

long sumAU = Sales.find("region", "AU").sum("amount");

long sumAuIt = Sales.find("region department", "AU", "IT").sum("amount");

最大值： 

long max = Sales._max("amount"); // also Sales.q().max("amount");

long maxIT = Sales.find("department", "IT").max("amount");

long maxAU = Sales.find("region", "AU").max("amount");

long maxAuIt = Sales.find("region department", "AU", "IT").max("amount");

最小值： 

long min = Sales._min("amount"); // also Sales.q().min("amount");

long minIT = Sales.find("department", "IT").min("amount");

long minAU = Sales.find("region", "AU").min("amount");

long minAuIt = Sales.find("region department", "AU", "IT").min("amount");

分组聚合:

每个聚合都会相应一个分组聚合的接口，就像SQL中的group by语句

分组计数：

// group by region

AggregationResult byRegion = Sales.groupCount("region");

System.out.println("AU count: " + byRegion.get("region", "AU");

// group by department

AggregationResult byDep = Sales.groupCount("department");

System.out.println("IT count: " + byDep.get("department", "IT");

// group by region and department

AggregationResult byRegionDep = Sales.groupCount("region, department");

System.out.println("IT count: " + byRegionDep.get("department, region", "IT", "AU");

分组求和： 

// group by region

AggregationResult byRegion = Sales.groupSum("region");

System.out.println("AU sum: " + byRegion.get("region", "AU");

// group by department

AggregationResult byDep = Sales.groupSum("department");

System.out.println("IT sum: " + byDep.get("department", "IT");

// group by region and department

AggregationResult byRegionDep = Sales.groupSum("region, department");

System.out.println("IT sum: " + byRegionDep.get("department, region", "IT", "AU");

分组求最大值： 

// group by region

AggregationResult byRegion = Sales.groupMax("region");

System.out.println("AU max: " + byRegion.get("region", "AU");

// group by department

AggregationResult byDep = Sales.groupMax("department");

System.out.println("IT max: " + byDep.get("department", "IT");

// group by region and department

AggregationResult byRegionDep = Sales.groupMax("region, department");

System.out.println("IT max: " + byRegionDep.get("department, region", "IT", "AU");

分组求最小值： 

// group by region

AggregationResult byRegion = Sales.groupMin("region");

System.out.println("AU min: " + byRegion.get("region", "AU");

// group by department

AggregationResult byDep = Sales.groupMin("department");

System.out.println("IT min: " + byDep.get("department", "IT");

// group by region and department

AggregationResult byRegionDep = Sales.groupMin("region, department");

System.out.println("IT min: " + byRegionDep.get("department, region", "IT", "AU");

原文链接：http://www.playframework.com/modules/morphia-1.2.9/statistics

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