How do i see elements in mongodb?

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How do I view entries in MongoDB?
How do I get the elements of an array in MongoDB?
How do I see all files in MongoDB?
How do I search for items in MongoDB?

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Match an Array
Query an Array for an Element
Specify Multiple Conditions for Array Elements
Additional Query Tutorials

➤ Use the Select your language drop-down menu in the upper-right to set the language of the following examples.

The following example queries for all documents where the field tags value is an array with exactly two elements, "red" and "blank", in the specified order:

If, instead, you wish to find an array that contains both the elements "red" and "blank", without regard to order or other elements in the array, use the $all operator:

The following example queries for all documents where tags is an array that contains the string "red" as one of its elements:

For example, the following operation queries for all documents where the array dim_cm contains at least one element whose value is greater than 25.

When specifying compound conditions on array elements, you can specify the query such that either a single array element meets these condition or any combination of array elements meets the conditions.

The following example queries for documents where the dim_cm array contains elements that in some combination satisfy the query conditions; e.g., one element can satisfy the greater than 15 condition and another element can satisfy the less than 20 condition, or a single element can satisfy both:

Use $elemMatch operator to specify multiple criteria on the elements of an array such that at least one array element satisfies all the specified criteria.

The following example queries for documents where the dim_cm array contains at least one element that is both greater than ($gt) 22 and less than ($lt) 30:

Using dot notation, you can specify query conditions for an element at a particular index or position of the array. The array uses zero-based indexing.

Note

When querying using dot notation, the field and nested field must be inside quotation marks.

The following example queries for all documents where the second element in the array dim_cm is greater than 25:

Use the $size operator to query for arrays by number of elements. For example, the following selects documents where the array tags has 3 elements.

For additional query examples, see:

Query Documents
Query on Embedded/Nested Documents
Query an Array of Embedded Documents

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$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: [, , ...  ] } }

For comparison of different BSON type values, see the specified BSON comparison order.

If the field holds an array, then the $in operator selects the documents whose field holds an array that contains at least one element that matches a value in the specified array (for example, , , and so on).

The $in operator compares each parameter to each document in the collection, which can lead to performance issues. To improve performance:

It is recommended that you limit the number of parameters passed to the $in operator to tens of values. Using hundreds of parameters or more can negatively impact query performance.
Create an index on the field you want to query.

Note

This document describes the $in query operator. For the $in aggregation operator, see $in (aggregation).

Create the inventory collection:

db.inventory.insertMany( [
   { "item": "Pens", "quantity": 350, "tags": [ "school", "office" ] },
   { "item": "Erasers", "quantity": 15, "tags": [ "school", "home" ] },
   { "item": "Maps", "tags": [ "office", "storage" ] },
   { "item": "Books", "quantity": 5, "tags": [ "school", "storage", "home" ] }
] )

Consider the following example:

db.inventory.find( { quantity: { $in: [ 5, 15 ] } }, { _id: 0 } )

This query selects all documents in the inventory collection where the value of the quantity field is either 5 or 15.

{ item: 'Erasers', quantity: 15, tags: [ 'school', 'home' ] },
{ item: 'Books', quantity: 5, tags: [ 'school', 'storage', 'home' ] }

Although you can write this query using the $or operator, use the $in operator rather than the $or operator when performing equality checks on the same field.

The following updateMany() operation sets the exclude field to false when the tags array has at least one element that matches either "home" or "school".

db.inventory.updateMany(
   { tags: { $in: [ "home", "school" ] } },
   { $set: { exclude: false } }
)

Example output:

{
   item: 'Pens',
   quantity: 350,
   tags: [ 'school', 'office' ],
   exclude: false
 },
 {
   item: 'Erasers',
   quantity: 15,
   tags: [ 'school', 'home' ],
   exclude: false
 },
 {
   item: 'Maps',
   tags: [ 'office', 'storage' ]
 },
 {
   item: 'Books',
   quantity: 5,
   tags: [ 'school', 'storage', 'home' ],
   exclude: false
 }

For additional examples in querying arrays, see:

Query an Array
Query an Array of Embedded Documents

For additional examples in querying, see:

Query Documents

The $in operator can specify matching values using regular expressions of the form /pattern/. You cannot use $regex operator expressions inside an $in.

Consider the following example:

db.inventory.find( { tags: { $in: [ /^be/, /^st/ ] } } )

This query selects all documents in the inventory collection where the tags field holds either a string that starts with be or st or an array with at least one element that starts with be or st.

Tip

How do I view entries in MongoDB?

If you want to check your databases list, use the command show dbs. Your created database (mydb) is not present in list. To display database, you need to insert at least one document into it. In MongoDB default database is test.

How do I get the elements of an array in MongoDB?

To search the array of object in MongoDB, you can use $elemMatch operator. This operator allows us to search for more than one component from an array object.

How do I see all files in MongoDB?

Using Java program Create a MongoDB client by instantiating the MongoClient class. Connect to a database using the getDatabase() method. Get the object of the collection from which you want to retrieve the documents, using the getCollection() method.

How do I search for items in MongoDB?

In MongoDB, find() method is used to select documents in a collection and return a cursor to the selected documents. Cursor means a pointer that points to a document, when we use find() method it returns a pointer on the selected documents and returns one by one.

programming mongodb In MongoDB And MongoDB elemMatch In mongoose Or MongoDB MongoDB find all MongoDB select fields

How do i see elements in mongodb?

Note

Note

Tip

How do I view entries in MongoDB?

How do I get the elements of an array in MongoDB?

How do I see all files in MongoDB?

How do I search for items in MongoDB?

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