MongoDB Common operations

Find method

Db.collection_name.find ();

Query all the results:

select * from Users;

Db.users.find ();

Specify which columns to return (key):

Select name, skills from users;

Db.users.find ({}, {' name ': 1, ' Skills ': 1});

Supplemental Note: The first {} places a Where condition the second {} Specifies that the columns are displayed and not displayed (0 indicates that no 1 is displayed)

Where Condition:

1. Simple equal To:

Select name, age, skills from users where name = ' hurry ';

Db.users.find ({' name ': ' Hurry '},{' name ': 1, ' age ': 1, ' Skills ': 1});

2. Using and

Select name, age, skills from users where name = ' hurry ' and age = 18;

Db.users.find ({' name ': ' Hurry ', ' age ': 18},{' name ': 1, ' age ': 1, ' Skills ': 1});

3. Use or

Select name, age, skills from users where name = ' hurry ' or age = 18;

Db.users.find ({' $or ': [{' name ': ' Hurry '}, {' Age ':}]},{' name ': 1, ' age ': 1, ' Skills ': 1});

4.<, <=, >= ($lt, $lte, $GT, $gte)

SELECT * from the users where age >= <= 30;

Db.users.find ({' age ': {' $gte ': ' $lte ': 30}});

5. In ($in, $nin) using in

SELECT * from the users where age in (10, 22, 26);

Db.users.find ({' age ': {' $in ': [10, 22, 26]}});

6. Matching NULL

SELECT * from users where-age is null;

Db.users.find ({' age ': null);

7.like (MongoDB supports regular expressions)

SELECT * from the users where name like "%hurry%";

Db.users.find ({name:/hurry/});

SELECT * from the users where name like "hurry%";

Db.users.find ({name:/^hurry/});

8. Use of distinct

Select DISTINCT (name) from users;

Db.users.distinct (' name ');

9. Use Count

Select COUNT (*) from users;

Db.users.count ();

10. Array query (MongoDB own special)

If skills is [' java ', ' Python ']

Db.users.find ({' Skills ': ' java '}); The statement can match a successful

$all

Db.users.find ({' skills ': {' $all ': [' java ', ' Python ']}}) skills must contain both Java and Python

$size

Db.users.find ({' skills ': {' $size ': 2}}) Unfortunately $size cannot be used in combination with $LT, etc.

$slice

Db.users.find ({' skills ': {' $slice: [1,1]}})

Two parameters are offset and number of returns

11. Query for embedded documents

12. Powerful $where query Db.foo.find ();
{"_id": ObjectId ("4e17ce0ac39f1afe0ba78ce4"), "a": 1, "B": 3, "C": 10}
{"_id": ObjectId ("4e17ce13c39f1afe0ba78ce5"), "a": 1, "B": 6, "C": 6}

What to do if you want to query for a document B = C.

> Db.foo.find ({"$where": function () {for (var.
For (Var other in this) {
if (current!= other && this[current] = = This[other]) {
return true;
}
}
}
return false;

}});

{"_id": ObjectId ("4e17ce13c39f1afe0ba78ce5"), "a": 1, "B": 6, "C": 6}

1). Greater than, less than, greater than or equal to, less than or equal to
$GT: Greater Than
$LT: Less than
$gte: greater than or equal to
$lte: Less than or equal to
Example:
Db.collection.find ({"field": {$gt: Value}}); Greater Than:field > value
Db.collection.find ({"field": {$lt: Value}}); Less Than:field < value
Db.collection.find ({"field": {$gte: Value}}); Greater than or equal To:field >= value
Db.collection.find ({"field": {$lte: Value}}); Less than or equal To:field <= value

If query J is greater than 3, less than 4:

Db.things.find ({j: {$lt: 3}});
Db.things.find ({j: {$gte: 4}});

You can also merge within a single statement:

Db.collection.find ({"field": {$gt: value1, $lt: value2}}); value1 < Field < value

2) is not equal to $ne

Example:

Db.things.find ({x: {$ne: 3}});

3) in and not in ($in $nin)
Grammar:
Db.collection.find ({"field": {$in: Array}});

Example: