How to fix IntegrityError: FOREIGN KEY constraint fails when deleting record... in Python
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We're excited to share with you our newest video, "How to solve IntegrityError: FOREIGN KEY constraint fails when deleting records linked via foreign keys in related tables. in Python". 🎥 This series is meticulously designed to arm you with knowledge 🧠 and skills 🛠️ to overcome frequent coding challenges.
Today, we will decipher 🔎 and resolve a common error faced by Python coders: the bit hard to solve IntegrityError: FOREIGN KEY constraint fails when deleting records linked via foreign keys in related tables.. Here is a snapshot of the code of the video:
Troubling Scenario: ❗️
import sqlite3
Create a database in RAM
db = sqlite3.connect(':memory:')
cursor = db.cursor()
Create tables
cursor.execute('''CREATE TABLE parent (id INTEGER PRIMARY KEY, name TEXT)''')
cursor.execute('''CREATE TABLE child (id INTEGER PRIMARY KEY, parent_id INTEGER, name TEXT,
FOREIGN KEY(parent_id) REFERENCES parent(id))''')
Insert data
cursor.execute('''INSERT INTO parent (id, name) VALUES (1, 'Parent1')''')
cursor.execute('''INSERT INTO child (id, parent_id, name) VALUES (1, 1, 'Child1')''')
db.commit()
Attempt to delete parent record while child record still exists
cursor.execute('''DELETE FROM parent WHERE id = 1''')
db.commit()
db.close()
Unwanted Result: 🚫
IntegrityError: FOREIGN KEY constraint fails when deleting records linked via foreign keys in related tables.
Effective Resolution: ✔️
import sqlite3
Create a database in RAM
db = sqlite3.connect(':memory:')
cursor = db.cursor()
Enable foreign key constraint
db.execute("PRAGMA foreign_keys = ON")
Create tables
cursor.execute('''CREATE TABLE parent (id INTEGER PRIMARY KEY, name TEXT)''')
cursor.execute('''CREATE TABLE child (id INTEGER PRIMARY KEY, parent_id INTEGER, name TEXT,
FOREIGN KEY(parent_id) REFERENCES parent(id))''')
Insert data
cursor.execute('''INSERT INTO parent (id, name) VALUES (1, 'Parent1')''')
cursor.execute('''INSERT INTO child (id, parent_id, name) VALUES (1, 1, 'Child1')''')
db.commit()
Delete child record first
cursor.execute('''DELETE FROM child WHERE parent_id = 1''')
Then delete parent record
cursor.execute('''DELETE FROM parent WHERE id = 1''')
db.commit()
db.close()
Desired Output: 🏁
No output.
In this detailed walkthrough, we will illuminate 💡 the underlying cause of this error, and offer a comprehensive explanation: Code1 fails due to attempting to delete a parent record with an existing child due to foreign key constraints. Code2 resolves this by deleting child records first, ensuring referential integrity. 🎯
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