我有一个问题,需要从两个集合中检索信息。 第一个集合存储员工信息:
{
"_id" : ObjectId("4f9643967f8b9a3f0a00005a"),
"birth_date" : "1963-09-09",
"departments" : [
{
"departments_id" : ObjectId("4f9643957f8b9a3f0a000007"),
"from_date" : "1990-01-03",
"to_date" : "1990-01-15"
}
],
"first_name" : "Parviz",
"gender" : "M",
"hire_date" : "1990-01-03",
"last_name" : "Lortz",
}
第二个是部门信息
{
"_id" : ObjectId("4f9643957f8b9a3f0a000004"),
"dept_name" : "Marketing",
"managers" : [
{
"employees_id" : ObjectId("4f96439b7f8b9a3f0a0186a9"),
"from_date" : "1985-01-01",
"to_date" : "1991-10-01"
},
{
"employees_id" : ObjectId("4f96439b7f8b9a3f0a0186aa"),
"from_date" : "1991-10-01",
"to_date" : "9999-01-01"
}
]
}
我尝试查找:给定员工的所有部门。
我尝试了类似以下的代码:
employees = db.employees.find({_id:ObjectId("some_id")});
db.departments.find({_id:{$in:...}});
但我不知道如何解释“ $in department_id of all departments from var employees”。