Create a view from mongo collection - mongodb

Question

I have a mongo collection with records like
and so on.
The sample record in JSON format
[{
empId:'123',
empName:'Emp1',
shiftHours:'Regular'
},
{
empId:'123',
empName:'Emp1',
shiftHours:'Morning'
}
]
Basically an employee can work in regular shift(9am-6 pm) or morning shift (6 am-3 pm) or night shift (9pm-6 am). The hours are just example here but the idea is that the working hours are categorized in 3 shifts. I want to create a view with flat structure per employee like this
and so on.
I am trying to understand what's the best way to create such a flat view (coming from SQL background, I think a procedure/function has to be written) but not sure what's the best way to do so using No-Sql (Mongo db).
Any suggestions?

Answer 1

$group by empId and conditionally $sum by shiftHours.
db.collection.aggregate([
{
$group: {
_id: "$empId",
empName: {
$first: "$empName"
},
Morning: {
$sum: {
"$cond": {
"if": {
$eq: [
"$shiftHours",
"Morning"
]
},
"then": 1,
"else": 0
}
}
},
Regular: {
$sum: {
"$cond": {
"if": {
$eq: [
"$shiftHours",
"Regular"
]
},
"then": 1,
"else": 0
}
}
},
Evening: {
$sum: {
"$cond": {
"if": {
$eq: [
"$shiftHours",
"Evening"
]
},
"then": 1,
"else": 0
}
}
}
}
},
{
$set: {
Morning: {
$cond: [
{
$gt: [
"$Morning",
0
]
},
"Y",
"N"
]
},
Regular: {
$cond: [
{
$gt: [
"$Regular",
0
]
},
"Y",
"N"
]
},
Evening: {
$cond: [
{
$gt: [
"$Evening",
0
]
},
"Y",
"N"
]
}
}
}
])
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