How do I know if a MySQL UPDATE query has completed because the information provided matches the data already in the database?

Question

I have a query when a user enters a block of text in the textarea field. They can store this information in a database. The problem is that if they have not changed the information or if the information matches the data already in the database, I get "0" for the affected rows. Usually I show an error saying that the request failed when there are no affected rows. How would I “know” that the rows affected by 0 are related to the fact that the data already exists, so that I can show a more specific error?

Answer 1

, 0 , - , UPDATE . :

UPDATE MyTable SET field = 'content' WHERE id = 1234;

0 , id = 1234. , UPDATE, .

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SELECT COUNT(*) FROM MyTable WHERE id = 1234;

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Answer 2

, MySQL ( 0). , 0 , 0.

PHP, - :

// ... mysql_query() with the UPDATE query

if (mysql_affected_rows() == 0 && mysql_errno() == 0)
{
    // Data was not changed
}