How to Prevent Duplicate Data Insertion in MySQL Using PHP?

Preventing Duplicate Data Insertion in MySQL Database

In a scenario where a MySQL table with columns id, pageId, and name needs to maintain unique combinations of pageId and name, preventing duplicate data insertion becomes crucial. This article explores the best practices for handling duplicate entries during data insertion using PHP.

Step 1: Create a Unique Index

To enforce uniqueness on the combination of pageId and name columns, an index can be created using the following SQL statement:

ALTER TABLE thetable ADD UNIQUE INDEX(pageid, name);

Step 2: Handling Duplicates

When a duplicate entry is encountered during insertion, the appropriate action can be determined based on specific requirements:

• Ignore the Duplicate: Utilizing the INSERT IGNORE statement allows the insertion process to continue without inserting the duplicate record.

INSERT IGNORE INTO thetable (pageid, name) VALUES (1, "foo"), (1, "foo");

• Overwrite the Existing Record: This can be achieved using an INSERT...ON DUPLICATE KEY UPDATE statement, where updating specific columns is specified in case a duplicate key is encountered.

INSERT INTO thetable (pageid, name, somefield)
VALUES (1, "foo", "first")
ON DUPLICATE KEY UPDATE (somefield = 'first')

INSERT INTO thetable (pageid, name, somefield)
VALUES (1, "foo", "second")
ON DUPLICATE KEY UPDATE (somefield = 'second')

• Update a Counter: If a duplicate record is considered a separate occurrence, a counter column can be incremented using the ON DUPLICATE KEY UPDATE syntax.

INSERT INTO thetable (pageid, name)
VALUES (1, "foo"), (1, "foo")
ON DUPLICATE KEY UPDATE (pagecount = pagecount + 1)

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