Referential Integrity in DBMS

What is Referential Integrity?

Example

CREATE TABLE fees (
  fee_id INT PRIMARY KEY,
  roll_no INT,
  FOREIGN KEY (roll_no) REFERENCES students(roll_no)
    ON DELETE CASCADE
);

ON DELETE / ON UPDATE

• CASCADE — change/delete children too.
• SET NULL — set the foreign key to NULL.
• RESTRICT — block the action if children exist.

Summary

• Referential integrity keeps foreign keys pointing to valid rows.
• ON DELETE CASCADE/SET NULL/RESTRICT control what happens to children.

Referential Integrity क्या है?

Example

CREATE TABLE fees (
  fee_id INT PRIMARY KEY,
  roll_no INT,
  FOREIGN KEY (roll_no) REFERENCES students(roll_no)
    ON DELETE CASCADE
);

ON DELETE / ON UPDATE

• CASCADE — children भी बदलें/हटाएं।
• SET NULL — foreign key NULL कर दें।
• RESTRICT — children हों तो action रोकें।

सारांश

• Referential integrity foreign keys को valid rows की ओर रखती है।
• ON DELETE CASCADE/SET NULL/RESTRICT children का behaviour control करते हैं।