mongodb-查询

1.查询子文档列表最后一条

sql

db.units_statistics_hourly.find({
    "unitNumber": "F8N9P141"
}, {
    "runDuration": {
        $slice: [ - 1, 1]
    },
    "runCounts": {
        $slice: [ - 1, 1]
    }
});

java

  public UnitStatisticsHourly getTotalPerformance(String unitNumber) {
    Criteria criteria = Criteria.where("unitNumber").is(unitNumber);
    Query query = Query.query(criteria);
    query.fields().slice("runDuration", -1, 1)
        .slice("runCounts", -1, 1);
    UnitStatisticsHourly totalPerformance = mongo
        .findOne(query, UnitStatisticsHourly.class, COLLECTION_PERFORMANCE_HOURLY_NAME);
    return totalPerformance;
  }