✅ SQL Constraints! 🛡️

SQL constraints are rules applied to table columns to maintain accurate and reliable data.

🔹 PRIMARY KEY
– Uniquely identifies each row
– No NULLs allowed

🔹 FOREIGN KEY
– Links to a primary key in another table
– Maintains referential integrity

🔹 UNIQUE
– Ensures all values in a column are different

🔹 NOT NULL
– Column must have a value (can’t be empty)

🔹 CHECK
– Restricts the values in a column
👉 Example: CHECK (age >= 18)

🔹 DEFAULT
– Sets a default value if none is provided

Constraints prevent bad data from entering your database 💾

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