In this article, integrating SQLite3 with Python is discussed. Here we will discuss all the CRUD operations on the SQLite3 database using Python. CRUD contains four major operations -
Note: This needs a basic understanding of SQL.
Here, we are going to connect SQLite with Python. Python has a native library for SQLite3 called sqlite3. Let us explain how it works.
Connecting to SQLite Database
- To use SQLite, we must import sqlite3.
import sqlite3
- Then create a connection using connect() method and pass the name of the database you want to access if there is a file with that name, it will open that file. Otherwise, Python will create a file with the given name.
sqliteConnection = sqlite3.connect('gfg.db')- After this, a cursor object is called to be capable to send commands to the SQL.
cursor = sqliteConnection.cursor()
Example: Connecting to SQLite3 database using Python
Python3 import sqlite3 # connecting to the database connection = sqlite3.connect("gfg.db") # cursor crsr = connection.cursor() # print statement will execute if there # are no errors print("Connected to the database") # close the connection connection.close() Output:
Connected to the database
Cursor Object
Before moving further to SQLite3 and Python let's discuss the cursor object in brief.
- The cursor object is used to make the connection for executing SQL queries.
- It acts as middleware between SQLite database connection and SQL query. It is created after giving connection to SQLite database.
- The cursor is a control structure used to traverse and fetch the records of the database.
- All the commands will be executed using cursor object only.
Executing SQLite3 Queries - Creating Tables
After connecting to the database and creating the cursor object let's see how to execute the queries.
- To execute a query in the database, create an object and write the SQL command in it with being commented. Example:- sql_comm = ”SQL statement”
- And executing the command is very easy. Call the cursor method execute() and pass the name of the sql command as a parameter in it. Save a number of commands as the sql_comm and execute them. After you perform all your activities, save the changes in the file by committing those changes and then lose the connection.
Example: Creating SQLite3 tables using Python
In this example, we will create the SQLite3 tables using Python. The standard SQL command will be used for creating the tables.
Python import sqlite3 # connecting to the database connection = sqlite3.connect("gfg.db") # cursor crsr = connection.cursor() # SQL command to create a table in the database sql_command = """CREATE TABLE emp ( staff_number INTEGER PRIMARY KEY, fname VARCHAR(20), lname VARCHAR(30), gender CHAR(1), joining DATE);""" # execute the statement crsr.execute(sql_command) # close the connection connection.close() Output:
Inserting into Table
To insert data into the table we will again write the SQL command as a string and will use the execute() method.
Example 1: Inserting Data into SQLite3 table using Python
Python3 # Python code to demonstrate table creation and # insertions with SQL # importing module import sqlite3 # connecting to the database connection = sqlite3.connect("gfg.db") # cursor crsr = connection.cursor() # SQL command to insert the data in the table sql_command = """INSERT INTO emp VALUES (23, "Rishabh",\ "Bansal", "M", "2014-03-28");""" crsr.execute(sql_command) # another SQL command to insert the data in the table sql_command = """INSERT INTO emp VALUES (1, "Bill", "Gates",\ "M", "1980-10-28");""" crsr.execute(sql_command) # To save the changes in the files. Never skip this. # If we skip this, nothing will be saved in the database. connection.commit() # close the connection connection.close() Output:
Example 2: Inserting data input by the user
Python3 # importing module import sqlite3 # connecting to the database connection = sqlite3.connect("gfg.db") # cursor crsr = connection.cursor() # primary key pk = [2, 3, 4, 5, 6] # Enter 5 students first names f_name = ['Nikhil', 'Nisha', 'Abhinav', 'Raju', 'Anshul'] # Enter 5 students last names l_name = ['Aggarwal', 'Rawat', 'Tomar', 'Kumar', 'Aggarwal'] # Enter their gender respectively gender = ['M', 'F', 'M', 'M', 'F'] # Enter their joining data respectively date = ['2019-08-24', '2020-01-01', '2018-05-14', '2015-02-02', '2018-05-14'] for i in range(5): # This is the q-mark style: crsr.execute('INSERT INTO emp VALUES ({pk[i]}, "{f_name[i]}", "{l_name[i]}", "{gender[i]}", "{date[i]}")') # To save the changes in the files. Never skip this. # If we skip this, nothing will be saved in the database. connection.commit() # close the connection connection.close() Output:
Fetching Data
In this section, we have discussed how to create a table and how to add new rows in the database. Fetching the data from records is simple as inserting them. The execute method uses the SQL command of getting all the data from the table using “Select * from table_name” and all the table data can be fetched in an object in the form of a list of lists.
Example: Reading Data from sqlite3 table using Python
Python # importing the module import sqlite3 # connect with the myTable database connection = sqlite3.connect("gfg.db") # cursor object crsr = connection.cursor() # execute the command to fetch all the data from the table emp crsr.execute("SELECT * FROM emp") # store all the fetched data in the ans variable ans = crsr.fetchall() # Since we have already selected all the data entries # using the "SELECT *" SQL command and stored them in # the ans variable, all we need to do now is to print # out the ans variable for i in ans: print(i) Output:
Note: It should be noted that the database file that will be created will be in the same folder as that of the python file. If we wish to change the path of the file, change the path while opening the file.
Updating Data
For updating the data in the SQLite3 table we will use the UPDATE statement. We can update single columns as well as multiple columns using the UPDATE statement as per our requirement.
UPDATE table_name SET column1 = value1, column2 = value2,… WHERE condition;
In the above syntax, the SET statement is used to set new values to the particular column, and the WHERE clause is used to select the rows for which the columns are needed to be updated.
Example: Updating SQLite3 table using Python
Python3 # Import module import sqlite3 # Connecting to sqlite conn = sqlite3.connect('gfg.db') # Creating a cursor object using # the cursor() method cursor = conn.cursor() # Updating cursor.execute('''UPDATE emp SET lname = "Jyoti" WHERE fname="Rishabh";''') # Commit your changes in the database conn.commit() # Closing the connection conn.close() Output:
Deleting Data
For deleting the data from the SQLite3 table we can use the delete command.
DELETE FROM table_name [WHERE Clause]
Example: Deleting from SQLite3 table using Python
Python3 # Import module import sqlite3 # Connecting to sqlite conn = sqlite3.connect('gfg.db') # Creating a cursor object using # the cursor() method cursor = conn.cursor() # Updating cursor.execute('''DELETE FROM emp WHERE fname="Rishabh";''') # Commit your changes in the database conn.commit() # Closing the connection conn.close() Output:
Deleting Table
DROP is used to delete the entire database or a table. It deleted both records in the table along with the table structure.
Syntax:
DROP TABLE TABLE_NAME;
Example: Drop SQLite3 table using Python
Total tables in the gfg.db before dropping
Now let's drop the Student table and then again check the total table in our database.
Python3 # Import module import sqlite3 # Connecting to sqlite conn = sqlite3.connect('gfg.db') # Creating a cursor object using # the cursor() method cursor = conn.cursor() # Updating cursor.execute('''DROP TABLE Student;''') # Commit your changes in the database conn.commit() # Closing the connection conn.close() Output:
Note: To learn more about SQLit3 with Python refer to our Python SQLite3 Tutorial.