Python SQLite - Where Clause

If you want to fetch, delete or, update particular rows of a table in SQLite, you need to use the where clause to specify condition to filter the rows of the table for the operation.
For example, if you have a SELECT statement with where clause, only the rows which satisfies the specified condition will be retrieved.
Following is the syntax of the WHERE clause in SQLite −
SELECT column1, column2, columnN
FROM table_name
WHERE [search_condition]

You can specify a search_condition using comparison or logical operators. like >, <, =, LIKE, NOT, etc. The following examples would make this concept clear.
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 SELECT statement retrieves the records whose age is greater than 35 −
sqlite> SELECT * FROM CRICKETERS WHERE AGE > 35;
First_Name Last_Name  Age  Place_Of_B Country
---------- ---------- ---- ---------- -------------
Jonathan   Trott      38   CapeTown   SouthAfrica
Kumara     Sangakkara 41   Matale     Srilanka
sqlite>

The Cursor object/class contains all the methods to execute queries and fetch data, etc. The cursor method of the connection class returns a cursor object.
Therefore, to create a table in SQLite database using python −
Establish connection with a database using the connect() method.
Establish connection with a database using the connect() method.
Create a cursor object by invoking the cursor() method on the above created connection object.
Create a cursor object by invoking the cursor() method on the above created connection object.
Now execute the CREATE TABLE statement using the execute() method of the Cursor class.
Now execute the CREATE TABLE statement using the execute() method of the Cursor class.
Following example creates a table named Employee and populates it. Then using the where clause it retrieves the records with age value less than 23.
import sqlite3

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

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

#Doping EMPLOYEE table if already exists.
cursor.execute("DROP TABLE IF EXISTS EMPLOYEE")
sql = '''CREATE TABLE EMPLOYEE(
   FIRST_NAME CHAR(20) NOT NULL,
   LAST_NAME CHAR(20),
   AGE INT,
   SEX CHAR(1),
   INCOME FLOAT
)'''
cursor.execute(sql)

#Populating the table
cursor.execute('''INSERT INTO EMPLOYEE(
   FIRST_NAME, LAST_NAME, AGE, SEX, INCOME) VALUES 
   ('Ramya', 'Rama priya', 27, 'F', 9000)''')

cursor.execute('''INSERT INTO EMPLOYEE
   (FIRST_NAME, LAST_NAME, AGE, SEX, INCOME) VALUES 
   ('Vinay', 'Battacharya', 20, 'M', 6000)''')

cursor.execute('''INSERT INTO EMPLOYEE(
   FIRST_NAME, LAST_NAME, AGE, SEX, INCOME) VALUES 
   ('Sharukh', 'Sheik', 25, 'M', 8300)''')

cursor.execute('''INSERT INTO EMPLOYEE(
   FIRST_NAME, LAST_NAME, AGE, SEX, INCOME) VALUES 
   ('Sarmista', 'Sharma', 26, 'F', 10000)''')

cursor.execute('''INSERT INTO EMPLOYEE(
   FIRST_NAME, LAST_NAME, AGE, SEX, INCOME) VALUES 
   ('Tripthi', 'Mishra', 24, 'F', 6000)''')

#Retrieving specific records using the where clause
cursor.execute("SELECT * from EMPLOYEE WHERE AGE <23")
print(cursor.fetchall())

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

#Closing the connection
conn.close()
[('Vinay', 'Battacharya', 20, 'M', 6000.0)]


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