Checking if a field contains a string

You can do it with the following code.

db.users.findOne({"username" : {$regex : "son"}});

---

As Mongo shell support regex, that's completely possible.

db.users.findOne({"username" : /.*son.*/});

If we want the query to be case-insensitive, we can use "i" option, like shown below:

db.users.findOne({"username" : /.*son.*/i});

See: http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-RegularExpressions

---

https://docs.mongodb.com/manual/reference/sql-comparison/

http://php.net/manual/en/mongo.sqltomongo.php

MySQL

SELECT * FROM users WHERE username LIKE "%Son%"

MongoDB

db.users.find({username:/Son/})

---

As of version 2.4, you can create a text index on the field(s) to search and use the $text operator for querying.

First, create the index:

db.users.createIndex( { "username": "text" } )

Then, to search:

db.users.find( { $text: { $search: "son" } } )

Benchmarks (~150K documents):

Regex (other answers) => 5.6-6.9 seconds

Text Search => .164-.201 seconds

Notes:

A collection can have only one text index. You can use a wildcard text index if you want to search any string field, like this: db.collection.createIndex( { "$**": "text" } ).

A text index can be large. It contains one index entry for each unique post-stemmed word in each indexed field for each document inserted.

A text index will take longer to build than a normal index.

A text index does not store phrases or information about the proximity of words in the documents. As a result, phrase queries will run much more effectively when the entire collection fits in RAM.

---

As this is one of the first hits in the search engines, and none of the above seems to work for MongoDB 3.x, here is one regex search that does work:

db.users.find( { 'name' : { '$regex' : yourvalue, '$options' : 'i' } } )

No need to create and extra index or alike.

---

Here's what you have to do if you are connecting MongoDB through Python

db.users.find({"username": {'$regex' : '.*' + 'Son' + '.*'}})

you may also use a variable name instead of 'Son' and therefore the string concatenation.

---

Simplest way to accomplish this task

If you want the query to be case-sensitive

db.getCollection("users").find({'username':/Son/})

If you want the query to be case-insensitive

db.getCollection("users").find({'username':/Son/i})

---

ideal answer its use index i option for case-insensitive

db.users.findOne({"username" : new RegExp(search_value, 'i') });

---

This should do the work

db.users.find({ username: { $in: [ /son/i ] } });

The i is just there to prevent restrictions of matching single cases of letters.

You can check the $regex documentation on MongoDB documentation. Here's a link: https://docs.mongodb.com/manual/reference/operator/query/regex/

---

I use this code and it work for search substring

db.users.find({key: { $regex: new RegExp(value, 'i')}})

---

If you need to do the search for more than one attribute you can use the $or. For example

Symbol.find(
  {
    $or: [
      { 'symbol': { '$regex': input, '$options': 'i' } },
      { 'name': { '$regex': input, '$options': 'i' } }
    ]
  }
).then((data) => {
  console.log(data)
}).catch((err) => {
  console.log(err)
})

Here you are basing your search on if the input is contained in the symbol attribute or the name attribute.

---

If the regex is not working in your Aggregate solution and you have nested object. Try this aggregation pipeline: (If your object structure is simple then, just remove the other conditions from below query):

db.user.aggregate({$match: 
     {$and:[
   {"UserObject.Personal.Status":"ACTV"},
   {"UserObject.Personal.Address.Home.Type":"HME"},
   {"UserObject.Personal.Address.Home.Value": /.*son.*/ }
   ]}}
   ) 

One other way would be to directly query like this:

db.user.findOne({"UserObject.Personal.Address.Home.Value": /.*son.*/ });

---

If your regex includes a variable, make sure to escape it.

function escapeRegExp(string) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}

This can be used like this

new RegExp(escapeRegExp(searchString), 'i')

Or in a mongoDb query like this

{ '$regex': escapeRegExp(searchString) }

Posted same comment here

---

For aggregation framework

Field search

('$options': 'i' for case insensitive search)

db.users.aggregate([
    {
        $match: {
            'email': { '$regex': '@gmail.com', '$options': 'i' }
        }
    }
]);

Full document search

(only works on fields indexed with a text index

db.articles.aggregate([
    {
        $match: { $text: { $search: 'brave new world' } }
    }
])

---

How to ignore HTML tags in a RegExp match:

var text = '<p>The <b>tiger</b> (<i>Panthera tigris</i>) is the largest <a href="/wiki/Felidae" title="Felidae">cat</a> <a href="/wiki/Species" title="Species">species</a>, most recognizable for its pattern of dark vertical stripes on reddish-orange fur with a lighter underside. The species is classified in the genus <i><a href="/wiki/Panthera" title="Panthera">Panthera</a></i> with the <a href="/wiki/Lion" title="Lion">lion</a>, <a href="/wiki/Leopard" title="Leopard">leopard</a>, <a href="/wiki/Jaguar" title="Jaguar">jaguar</a>, and <a href="/wiki/Snow_leopard" title="Snow leopard">snow leopard</a>. It is an <a href="/wiki/Apex_predator" title="Apex predator">apex predator</a>, primarily preying on <a href="/wiki/Ungulate" title="Ungulate">ungulates</a> such as <a href="/wiki/Deer" title="Deer">deer</a> and <a href="/wiki/Bovid" class="mw-redirect" title="Bovid">bovids</a>.</p>';
var searchString = 'largest cat species';

var rx = '';
searchString.split(' ').forEach(e => {
  rx += '('+e+')((?:\\s*(?:<\/?\\w[^<>]*>)?\\s*)*)';
});

rx = new RegExp(rx, 'igm');

console.log(text.match(rx));

This is probably very easy to turn into a MongoDB aggregation filter.

---