When working with textual data in mongodb, you may want to fetch documents with partial match on a field. You can use the $regex operator in mongodb for running like queries. By default, the like query using $regex is case sensitive.

Assume that you have collection in your mongodb containing names of the countries. A sample document from the countries collection is given below,

{
  "countryName" : "United States",
  "isoCode" : "US",
  "countryCode" : "1"
}

The following mongodb query fetches all documents where countryName contains "rab" anywhere. This query is the SQL equivalent of "%rab%".

db.getCollection('countries').find({'countryName': {'$regex': 'rab'}})

The above query returns documents for "United Arab Emirates" and "Saudi Arabia". But if you replace "rab" with "RAB", not document is returned. For doing a case-insensitive search, you need to use the $options for $regex as given below.

db.getCollection('countries').find({'countryName': {'$regex': 'RAB', '$options':'i'}})

The above query returns documents for "United Arab Emirates" and "Saudi Arabia" by doing a case-insensitive search.

Run the following query if you want to retrieve all the countries where the name starts with "In" by doing a case-insensitive search.

db.getCollection('countries').find({'countryName': {'$regex': '^In', '$options':'i'}})

Run the following query to retrieve all the countries where the name ends with "tes" by doing a case-insensitive search.

db.getCollection('countries').find({'countryName': {'$regex': "tes$"
, '$options':'i'}})