TinyDB - Logical Negate

Logical Negate works as an inverse logical gate. It will match the documents that don t match the given query. In simple words, it will display the opposite meaning of the given command.

Syntax

The syntax of TinyDB Logical Negate is as follows −

db.search(~(Query().field)

Here, field represents the part of data that we want to access. Query() is the object created of our JSON table named student. It will fetch the data that represents the opposite meaning of the given command.

Let s take a couple of examples and see how it works. We will use the same student database that we have used in all the previous chapters.

Example 1

Let s see how we can find the fields from our student table where the student name is not elen −

from tinydb import TinyDB, Query
db = TinyDB( student.json )
db.search(~(Query().st_name ==  elen ))

The above query will fetch all the rows where the student name is not "elen".

[
   {
      "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"
   }
]

Example 2

Let s see how we can avoid a particular address using logical negate −

from tinydb import TinyDB, Query
db = TinyDB( student.json )
db.search(~(student.address.one_of([ keral ,  delhi ])))

This query will fetch all the rows where the "address" field does not have either "keral" or "delhi".

[
   {
      "roll_number":4,
      "st_name":"lakan",
      "mark":200,
      "subject":"MySQL",
      "address":"mumbai"
   },
   {
      "roll_number":5,
      "st_name":"karan",
      "mark":275,
      "subject":"TinyDB",
      "address":"benglore"
   }
]