TinyDB - Retrieve Data

There are numerous ways with the help of which you can retrieve data from a TinyDB database. But to use those ways, you first need to create an instance of the Query class as follows −

from tinydb import Query
Student = Query()

Here, Student is the name of the database.

Let s check the various ways to retrieve the information from a TinyDB database.

Data Retrieval Using the Search() Method

The search() method, as its name imppes, returns the pst of items that mathches the query we provided, otherwise it will return an empty pst.

For this and other examples, we will be using the following student database data −

[
   {
      "roll_number": 1,
      "st_name": "elen",
      "mark": 250,
      "subject": "TinyDB",
      "address": "delhi"
   },
   {
      "roll_number": 2,
      "st_name": "Ram",
      "mark": [
         250,
         280
      ],
      "subject": [
         "TinyDB",
         "MySQL"
      ],
      "address": "delhi"
   },
   {
      "roll_number": 3,
      "st_name": "kevin",
      "mark": [
         180,
         200
      ],
      "subject": [
         "oracle",
         "sql"
      ],
      "address": "keral"
   },
   {
      "roll_number": 4,
      "st_name": "lakan",
      "mark": 200,
      "subject": "MySQL",
      "address": "mumbai"
   },
   {
      "roll_number": 5,
      "st_name": "karan",
      "mark": 275,
      "subject": "TinyDB",
      "address": "benglore"
   }
]

Let s take an example to understand the search() method −

from tinydb import TinyDB, Query
db = TinyDB("leekha.json")
student = Query()
db.search(student.subject ==  TinyDB  )

The above query will retrieve the the following output from the student database −

[
   {
      "roll_number":1,
      "st_name":"elen",
      "mark":250,
      "subject":"TinyDB",
      "address":"delhi"
   },
   {
      "roll_number":5,
      "st_name":"karan",
      "mark":275,
      "subject":"TinyDB",
      "address":"benglore"
   }
]

Data Retrieval Using the get() Method

As opposed to the search() method, the get() method returns only one matching document. It will return None, otherwise. For example, let s take the following code −

from tinydb import TinyDB, Query
student = Query()
db.get(student.subject ==  TinyDB  )

The above query will retrieve the following data from the student database.

[{ roll_number : 1,  st_name :  elen ,  mark : 250,  subject :  TinyDB ,  address :  delhi }]

Data Retrieval using the all() Method

The all() method returns all the documents in the database. For example,

db.all()

It will retrieve the entire data from the student database.

[
   {
      "roll_number":1,
      "st_name":"elen",
      "mark":250,
      "subject":"TinyDB",
      "address":"delhi"
   },
   {
      "roll_number":2,
      "st_name":"Ram",
      "mark":[
         250,
         280
      ],
      "subject":[
         "TinyDB",
         "MySQL"
      ],
      "address":"delhi"
   },
   {
      "roll_number":3,
      "st_name":"kevin",
      "mark":[
         180,
         200
      ],
      "subject":[
         "oracle",
         "sql"
      ],
      "address":"keral"
   },
   {
      "roll_number":4,
      "st_name":"lakan",
      "mark":200,
      "subject":"MySQL",
      "address":"mumbai"
   },
   {
      "roll_number":5,
      "st_name":"karan",
      "mark":275,
      "subject":"TinyDB",
      "address":"benglore"
   }
]

Data Retrieval Using the for Loop

The for loop also returns all the documents in the database. For example,

for info in db:
   print(info)

Just pke the all() method, it will retrieve all the rows from the student database.