Deleting Data from Table

Let us understand how data is deleted using DELETE statement.

  • Delete statement will have optional WHERE clause where we specify the condition to filter for rows that need to be deleted.

  • As part of the WHERE clause generally we will have indexed column for performance reasons.

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%run 05_function_get_database_connection.ipynb

%load_ext sql

%env DATABASE_URL=postgresql://itversity_sms_user:sms_password@localhost:5432/itversity_sms_db

%%sql 

SELECT user_id, 
    user_password 
FROM users

# DELETE FROM users WHERE user_password IS NULL OR user_id = 4

cursor = sms_connection.cursor()
query = ("""
    DELETE FROM users
    WHERE user_password IS NULL OR user_id = %s
""")

cursor.execute(query, (4,))
sms_connection.commit()
sms_connection.close()

%%sql 

SELECT user_id, user_password FROM users
Update Existing Table Data Querying Data From Table