Query using $dateFromString and $lt and $lge in mongodb - mongodb

Question

I am trying to return some records for date range from mongodb and I am trying to use the following query to query the collection test for the field StartDate:
db.test.aggregate([
{
$match: {
"StartDate": {
"$gte": [
{
"$dateFromString": {
"dateString": "2021-03-01T00:00:00.0000000Z"
}
}
],
"$lt": [
{
"$dateFromString": {
"dateString": "2021-04-01T00:00:00.0000000Z"
}
}
]
}
}
}
])
The above query didn't return anything but I am sure there are some data between the dates. Any ideas what have I missed? Thanks!

Answer 1

The $dateFromString is a aggregation pipeline operator, so it requires to match in $expr expression condition, and expression have different syntax of $gte and $lt,
db.test.aggregate([
{
$match: {
$expr: {
$and: [
{
$gte: [
"$StartDate",
{
"$dateFromString": {
"dateString": "2021-03-01T00:00:00.0000000Z"
}
}
]
},
{
$lt: [
"$StartDate",
{
"$dateFromString": {
"dateString": "2021-04-01T00:00:00.0000000Z"
}
}
]
}
]
}
}
}
])
Playground
Second option: You can use $toDate operator alternate of $dateFromString,
Playground
Update as per new requirement:
Field activities.dateOfActivity is an array, it requires to iterate through loop and check each date's conditions,
$map to iterate loop of activities.dateOfActivity array and put both condition inside, it will return true if both condition satisfy otherwise return false
$anyElementTrue will check return array of boolean have any true condition then return document
db.test.aggregate([
{
$match: {
$and: [
{
"$expr": {
$anyElementTrue: {
$map: {
input: "$activities.dateOfActivity",
in: {
$and: [
{
"$gte": [
"$$this",
{
"$dateFromString": {
"dateString": "2021-03-01T00:00:00.0000000Z"
}
}
]
},
{
"$lt": [
"$$this",
{
"$dateFromString": {
"dateString": "2021-04-20T00:00:00.0000000Z"
}
}
]
}
]
}
}
}
}
}
]
}
}
])
Playground