This document summarizes various MongoDB array query and update operators. It provides examples of using the $all, $elemMatch, $in, and $ operators to query or update array fields. The $all operator matches arrays containing all specified elements. $elemMatch matches arrays containing an element matching a sub-query. $in selects arrays containing an element equal to any in the specified array. The $ operator acts as a placeholder when updating the first matched array element by position.

1. /*************************Query Operator Array**************************/
Name Description
$all Matches arrays that contain all elements specified in
the query.
$elemMatch Selects documents if element in the array field matches
all the specified
$elemMatch conditions.
$size Selects documents if the array field is a specified
size.
$all
The $all operator selects the documents where the value of a field is an array
that contains all the
specified elements. To specify an $all expression, use the following prototype:
{ <field>: { $all: [ <value1> , <value2> ... ] } }
db.inventory.insert([
{
_id: 1,
code: "xyz",
tags: [ "school", "book", "bag", "headphone", "appliance" ],
qty: [
{ size: "S", num: 10, color: "blue" },
{ size: "M", num: 45, color: "blue" },
{ size: "L", num: 100, color: "green" }
]
},
{
_id: 2,
code: "abc",
tags: [ "appliance", "school", "book" ],
qty: [
{ size: "6", num: 100, color: "green" },
{ size: "6", num: 50, color: "blue" },
{ size: "8", num: 100, color: "brown" }
]
},
{
_id: 3,
code: "efg",
tags: [ "school", "book" ],
qty: [
{ size: "S", num: 10, color: "blue" },
{ size: "M", num: 100, color: "blue" },
{ size: "L", num: 100, color: "green" }
]
},
{
_id: 4,
code: "ijk",
tags: [ "electronics", "school" ],
qty: [
{ size: "M", num: 100, color: "green" }
]
}]
);
db.inventory.find({ "tags.0": "school" })

2. Use $all to Match Values
________________________________
The following operation uses the $all operator to query the inventory collection
for documents where
the value of the tags field is an array whose elements include appliance,
school, and book:
db.collection.find({},{})
db.inventory.find( { tags: { $all: [ "appliance", "school", "book" ] } } )
$gt
$or
$inc
$lte
$toUpper
Use $all with $elemMatch
________________________________
If the field contains an array of documents, you can use the $all with the
$elemMatch operator.
The below operation queries the inventory collection for documents where the
value of the
qty field is an array whose elements match the $elemMatch criteria:
db.inventory.find( {
qty: { $all: [
{ "$elemMatch" : { size: "M", num: { $lt:
50} } },
{ "$elemMatch" : { num : 100, color: "green"
} }
] }
} )
db.inventory.find( {
qty: { $all: [
{ "$elemMatch" : { size: "M", num: { $gt: 50} } },
{ "$elemMatch" : { num : 100, color: "green" } }
] }
} )
db.inventory.find( { "qty.num": { $all: [ 50,100 ] } } )
db.inventory.find( { "qty.num" : 50 } )
$elemMatch (query)
_________________________________
The $elemMatch operator matches documents that contain an array field with at
least one element that matches all the specified query criteria.
{ <field>: { $elemMatch: { <query1>, <query2>, ... } } }

3. db.score.insert([
{ _id: 1, results: [ 82, 85, 88 ] },
{ _id: 2, results: [ 75, 88, 89 ] }
])
db.score.find(
{ results: { $elemMatch: { $gte: 80, $lt: 85 } } }
)
Array of Embedded Documents
___________________________
db.survey.insert([
{ _id: 1, results: [ { product: "abc", score: 10 }, { product: "xyz", score: 5 }
] },
{ _id: 2, results: [ { product: "abc", score: 8 }, { product: "xyz", score:
7 } ] },
{ _id: 3, results: [ { product: "abc", score: 7 }, { product: "xyz", score:
8 } ] }
])
db.survey.find(
{ results: { $elemMatch: { product: "xyz", score: { $gte: 8 } } } }
)
db.survey.find(
{ "results.product": "xyz" }
)
/***************************Operators ***********************************/
$in
The $in operator selects the documents where the value of a field equals any
value in the specified array.
To specify an $in expression, use the following prototype:
{ field: { $in: [<value1>, <value2>, ... <valueN> ] } }
db.employee.find( { employee_id: { $in: [ 50002, 50004 ] } } )
/************************************************************************/
db.inventory.insert([
{ _id: 1, item: { name: "ab", code: "123" }, qty: 15, tags: [ "A", "B", "C" ] },
{ _id: 2, item: { name: "cd", code: "123" }, qty: 20, tags: [ "B" ] },
{ _id: 3, item: { name: "ij", code: "456" }, qty: 25, tags: [ "A", "B" ] },
{ _id: 4, item: { name: "xy", code: "456" }, qty: 30, tags: [ "B", "A" ] },
{ _id: 5, item: { name: "mn", code: "000" }, qty: 20, tags: [ [ "A", "B" ],
"C" ] }
])
Equals a Specified Value
________________________
1. db.inventory.find( { qty: { $eq: 20 } } ).pretty()

4. Field in Embedded Document Equals a Value
__________________________________________
2. db.inventory.find( { "item.name": { $eq: "ab" } } ).pretty()
Array Element Equals a Value
____________________________
/*********** Issue *************************/
3. db.inventory.find( { tags: { $eq: "B" } } )
Equals an Array Value
_____________________
db.inventory.find( { tags: { $eq: [ "A", "B" ] } } )
/**************************Array Update Operators
*********************************/
1. Update Operators
2. Update Operator Modifiers
3. Update Operators
Name Description
$ Acts as a placeholder to update the first element that
matches the query condition in an update.
$addToSet Adds elements to an array only if they do not already exist in
the set.
$pop Removes the first or last item of an array.
$pullAll Removes all matching values from an array.
$pull Removes all array elements that match a specified query.
$pushAll Deprecated. Adds several items to an array.
$push Adds an item to an array.
Update Operator Modifiers
Name Description
$each Modifies the $push and $addToSet operators to append multiple
items for array updates.
$slice Modifies the $push operator to limit the size of updated
arrays.
$sort Modifies the $push operator to reorder documents stored in an
array.
$position Modifies the $push operator to specify the position in the
array to add elements.
$ (update)
_________________
Update Values in an Array
_________________________
db.student.insert(
[
{ "_id" : 1, "grades" : [ 80, 85, 90 ] },
{ "_id" : 2, "grades" : [ 88, 90, 92 ] },
{ "_id" : 3, "grades" : [ 85, 100, 90 ] }
]
)
To update 80 to 82 in the grades array in the first document,
use the positional $ operator if you do not know the position of the element in

5. the array:
db.student.update(
{ _id: 1, "grades": 80 },
{ $set: { "grades.1" : 82 } }
)
Note: Remember that the positional $ operator acts as a placeholder for the
first match of the update query

6. the array:
db.student.update(
{ _id: 1, "grades": 80 },
{ $set: { "grades.1" : 82 } }
)
Note: Remember that the positional $ operator acts as a placeholder for the
first match of the update query