Can $in and $or replace each other in MongoDB? - database

Question

Can $in and $or replace each other in MongoDB?
db.restaurants.find(
{
"borough" :{$in :["Staten Island","Queens","Bronx","Brooklyn"]}},
{
"restaurant_id" : 1,
"name":1,"borough":1,
"cuisine" :1
}
);
db.restaurants.find(
{
"borough": "Bronx" ,
$or : [
{ "cuisine" : "American " },
{ "cuisine" : "Chinese" }
]
}
);
Here I observe that both these queries require us to choose from some options:
Does it make sense to replace $in in the first query with $or as follows:
db.restaurants.find(
{ $or: [{ borough: 'Staten Island',
borough: 'Queens',
borough: 'Bronx',
borough: 'Brooklyn' }],
{ _id : 1,
name: 1,
borough : 1,
cuisine : 1
}
})
Are $in and $or replaceable?
Update:
I tried to use two queries in a hope to get identical results:
Why is the second query selecting two rows of status 'D' only?
> db.inventory.find( {status : { $in: [ 'A', 'D'] }}, {item:1, status: 1})
{ "_id" : ObjectId("5eb67598bee5213484d45087"), "item" : "journal", "status" : "A" }
{ "_id" : ObjectId("5eb67598bee5213484d45088"), "item" : "notebook", "status" : "A" }
{ "_id" : ObjectId("5eb67598bee5213484d45089"), "item" : "paper", "status" : "D" }
{ "_id" : ObjectId("5eb67598bee5213484d4508a"), "item" : "planner", "status" : "D" }
{ "_id" : ObjectId("5eb67598bee5213484d4508b"), "item" : "postcard", "status" : "A" }
>
>
> db.inventory.find( {$or: [ {status: 'A', status: 'D'} ] }, {item:1, status: 1})
{ "_id" : ObjectId("5eb67598bee5213484d45089"), "item" : "paper", "status" : "D" }
{ "_id" : ObjectId("5eb67598bee5213484d4508a"), "item" : "planner", "status" : "D" }
>

Answer 1

From their official documentation itself or-versus-in :
When using $or with that are equality checks for the
value of the same field, use the $in operator instead of the $or
operator.
If you've docs like below :
[
{
"price": 100
},
{
"price": 200
},
{
"price": 300
},
{
"price": 400
},
{
"price": 500
}
]
If you wanted to get docs where price is equal to 100 or 500, query like :
db.collection.find({ price: { $in: [ 100, 500 ] } })
By doing like above, query is simple & clean. You can also use $or instead of $in but why would you loose shorthand notation and try to make your query look bulky by adding more objects of same field again and again ?
By default if you wanted to do logical OR on two different operators you would use $or, But when to use $or on same field :
db.collection.find({ $or: [ { price: { $lt: 200 } }, { price: { $gt: 400 } } ] })
As like above when you've multiple different conditions to match on same field you'll use it.
These two queries yield same result when executed but when you use $in - if input values are straight numbers or can be strings or other types where input values will exactly match with values of price field in docs, but when you use $or you're checking for different conditions on same field.
Test : mongoplayground