我正在尝试查询mongodb中的一个集合：
我想了解警察局警长的人数？
我的代码 -
db.EMPDETAILS.find({$and: [{Job Titles: "SERGEANT"}, {Department: "POLICE"}]}).count()
表结构如下所示 - （mongo导入了csv文件 - ） -
> db.EMPDETAILS.find()
{ "_id" : ObjectId("5927455eb048747c01baa981"), "Name" : "ALLISON, PAUL W", "Job Titles" : "LIEUTENANT", "Department" : "FIRE", "Full or Part-Time" : "F", "Salary or Hourly" : "Salary", "Typical Hours" : "", "Annual Salary" : "$107790.00", "Hourly Rate" : "" }
{ "_id" : ObjectId("5927455eb048747c01baa982"), "Name" : "BRUNO, KEVIN D", "Job Titles" : "SERGEANT", "Department" : "POLICE", "Full or Part-Time" : "F", "Salary or Hourly" : "Salary", "Typical Hours" : "", "Annual Salary" : "$104628.00", "Hourly Rate" : "" }
{ "_id" : ObjectId("5927455eb048747c01baa983"), "Name" : "COOPER, JOHN E", "Job Titles" : "LIEUTENANT-EMT", "Department" : "FIRE", "Full or Part-Time" : "F", "Salary or Hourly" : "Salary", "Typical Hours" : "", "Annual Salary" : "$114324.00", "Hourly Rate" : "" }
{ "_id" : ObjectId("5927455eb048747c01baa984"), "Name" : "CRESPO, VILMA I", "Job Titles" : "STAFF ASST", "Department" : "LAW", "Full or Part-Time" : "F", "Salary or Hourly" : "Salary", "Typical Hours" : "", "Annual Salary" : "$76932.00", "Hourly Rate" : "" }
{ "_id" : ObjectId("5927455eb048747c01baa985"), "Name" : "DOLAN, ROBERT J", "Job Titles" : "SERGEANT", "Department" : "POLICE", "Full or Part-Time" : "F", "Salary or Hourly" : "Salary", "Typical Hours" : "", "Annual Salary" : "$111474.00", "Hourly Rate" : "" }
{ "_id" : ObjectId("5927455eb048747c01baa986"), "Name" : "DUBERT, TOMASZ ", "Job Titles" : "PARAMEDIC I/C", "Department" : "FIRE", "Full or Part-Time" : "F", "Salary or Hourly" : "Salary", "Typical Hours" : "", "Annual Salary" : "$91080.00", "Hourly Rate" : "" }
{ "_id" : ObjectId("5927455eb048747c01baa987"), "Name" : "EDWARDS, TIM P", "Job Titles" : "LIEUTENANT", "Department" : "FIRE", "Full or Part-Time" : "F", "Salary or Hourly" : "Salary", "Typical Hours" : "", "Annual Salary" : "$114846.00", "Hourly Rate" : "" }
我是MongoDB的新手。任何帮助将不胜感激。