Mongoose and sql comparison - sql

Question

This is a multi question
From a mongoose result I have several items in the result which I get through result.length.
How can I get specific items e.g.
Person.find({'exployment.office':'Greenway'})
.exec(function(err, result){
//from the result, how can i get those items with
result.length would give me the number of items in the result
but how can i get a specific item without having to use loop to get
the specific item within the result
//There are like fifty people in the result,
//how can i get the number of items in result
});
In SQL, I have a query like this
select *
from table1, table2
where table2.field2 = value1
and table2.field2 = table1.field2
and table1.value1 = value3
e.g.
select *
from city, state
where state.name = 'xxy'
and state.id = city.state_id
and city.name != 'yyy'
How can this be converted to mongoose?
In SQL if I want to select people whose first name are e.g. Smith, Queen I can use things like
select *
from table
where first_name in (Smith, Queen)
This would give me result for people whose first_name matches SMith and Queen
How can I do this in mongoose?

Answer 1

select *
from Person
where first_name in (Smith, Queen)
Would simply be this using $in:
Person.find({'first_name': { $in: ['Smith', 'Queen']}}) ...
Next one:
select *
from city, state
where state.name = 'xxy'
and state.id = city.state_id
and city.name != 'yyy'
Using mongoose, you would need to use populate and create the schemas with ref relationships.
City.find({ "name": { $ne: "yyy"} }).populate({
"path": "state",
"match": { "state.name": "xxy" }
}) ...
Next one:
Person.find({'exployment.office':'Greenway'})
.exec(function(err, result){
//from the result, how can i get those items with
result.length would give me the number of items in the result
but how can i get a specific item without having to use loop to get
the specific item within the result
//There are like fifty people in the result,
//how can i get the number of items in result
});
You would filter as much as you can before you exec the query to get the records you need rather than filter after you get all in the result. result.length sure would give you the count although you could get the count via something like this;
Person.count({first_name: "Smith"}).exec() ...