Python SQLite - Delete Data

Advertisements

Previous Page
Next Page  

To delete records from a SQLite table, you need to use the DELETE FROM statement. To remove specific records, you need to use WHERE clause along with it.

Syntax

Following is the syntax of the DELETE query in SQLite −

DELETE FROM table_name [WHERE Clause]

Example

Assume we have created a table with name CRICKETERS using the following query −

sqlite> CREATE TABLE CRICKETERS (
   First_Name VARCHAR(255),
   Last_Name VARCHAR(255),
   Age int,
   Place_Of_Birth VARCHAR(255),
   Country VARCHAR(255)
);
sqlite>

And if we have inserted 5 records in to it using INSERT statements as −

sqlite> insert into CRICKETERS values('Shikhar', 'Dhawan', 33, 'Delhi', 'India');
sqlite> insert into CRICKETERS values('Jonathan', 'Trott', 38, 'CapeTown', 'SouthAfrica');
sqlite> insert into CRICKETERS values('Kumara', 'Sangakkara', 41, 'Matale', 'Srilanka');
sqlite> insert into CRICKETERS values('Virat', 'Kohli', 30, 'Delhi', 'India');
sqlite> insert into CRICKETERS values('Rohit', 'Sharma', 32, 'Nagpur', 'India');
sqlite>

Following statement deletes the record of the cricketer whose last name is 'Sangakkara'.

sqlite> DELETE FROM CRICKETERS WHERE LAST_NAME = 'Sangakkara';
sqlite>

If you retrieve the contents of the table using the SELECT statement, you can see only 4 records since we have deleted one.

sqlite> SELECT * FROM CRICKETERS;
First_Name   Last_Name    Age    Place_Of_B   Country
----------   ----------   ----   ----------   --------
Shikhar      Dhawan       46     Delhi        India
Jonathan     Trott        39     CapeTown     SouthAfrica
Virat        Kohli        31     Delhi        India
Rohit        Sharma       33     Nagpur       India
sqlite>

If you execute the DELETE FROM statement without the WHERE clause, all the records from the specified table will be deleted.

sqlite> DELETE FROM CRICKETERS;
sqlite>

Since you have deleted all the records, if you try to retrieve the contents of the CRICKETERS table, using SELECT statement you will get an empty result set as shown below −

sqlite> SELECT * FROM CRICKETERS;
sqlite>

Deleting Data Using Python

To add records to an existing table in SQLite database −

  • Import sqlite3 package.

  • Create a connection object using the connect() method by passing the name of the database as a parameter to it.

  • The cursor() method returns a cursor object using which you can communicate with SQLite3. Create a cursor object by invoking the cursor() object on the (above created) Connection object.

  • Then, invoke the execute() method on the cursor object, by passing an DELETE statement as a parameter to it.

Example

Following python example deletes the records from EMPLOYEE table with age value greater than 25.

import sqlite3
#Connecting to sqlite
conn = sqlite3.connect('example.db')

#Creating a cursor object using the cursor() method
cursor = conn.cursor()

#Retrieving contents of the table
print("Contents of the table: ")
cursor.execute('''SELECT * from EMPLOYEE''')
print(cursor.fetchall())

#Deleting records
cursor.execute('''DELETE FROM EMPLOYEE WHERE AGE > 25''')

#Retrieving data after delete
print("Contents of the table after delete operation ")
cursor.execute("SELECT * from EMPLOYEE")
print(cursor.fetchall())

#Commit your changes in the database
conn.commit()

#Closing the connection
conn.close()

Output

Contents of the table:
[
   ('Ramya', 'Rama priya', 27, 'F', 9000.0), 
   ('Vinay', 'Battacharya', 21, 'M', 6000.0), 
   ('Sharukh', 'Sheik', 26, 'M', 8300.0), 
   ('Sarmista', 'Sharma', 26, 'F', 10000.0), 
   ('Tripthi', 'Mishra', 24, 'F', 6000.0)
]
Contents of the table after delete operation
[
   ('Vinay', 'Battacharya', 21, 'M', 6000.0), 
   ('Tripthi', 'Mishra', 24, 'F', 6000.0)
]
Advertisements