In databases, primary keys are oftenset to auto-incrementso that new rows automatically receive unique values. However,one common error is manually inserting a value into an auto-incremented primary key column, whichoverrides the automatic numberingand may cause conflicts.
Example of Auto-Increment Setup:
sql
CREATE TABLE Users (
UserID INT AUTO_INCREMENT PRIMARY KEY,
Username VARCHAR(50)
);
Incorrect Insert (Error-Prone Approach):
sql
INSERT INTO Users (UserID, Username) VALUES (100, 'Alice');
Thismanually overrides the auto-increment, which can lead toduplicate key errors.
Correct Insert (Avoiding Errors):
sql
INSERT INTO Users (Username) VALUES ('Alice');
Thedatabase assigns UserID automatically, preventing conflicts.
Why Other Options Are Incorrect:
Option B (Failing to set a numeric value) (Incorrect):The databaseautomatically assignsvalues when AUTO_INCREMENT is used.
Option C (Designating multiple primary keys) (Incorrect):Whileincorrect, most databases will prevent this at creation time.
Option D (Forgetting to specify which is the auto-increment column) (Incorrect):If AUTO_INCREMENT is set, the database handles numbering automatically.
Thus, the most common error isInserting a value and overriding auto-increment, which can causeduplicate key errors and data inconsistencies.