Why Are My MySQLi Prepared Statements with the IN Operator Returning No Results?

MySQLi Prepared Statements with the IN Operator

Developers frequently encounter the need to query a database using the IN operator to retrieve specific rows based on a set of values. While using prepared statements is a recommended practice to prevent SQL injection, some users have reported encountering difficulties when attempting to use prepared statements with the IN operator. This article delves into a specific case where data retrieval using prepared statements and the IN operator returned no results, despite the existence of the desired data in the database.

In the example provided, the developer had prepared a statement that attempted to select rows from the 'users' table where the 'lastname' column matched one of a set of values provided in an array. The preparation process involved binding a string containing the comma-separated values to the prepared statement. However, the query returned an empty result set, even though the values existed in the database.

Upon further investigation, the developer discovered that the issue lay in the manner in which the parameter was bound to the prepared statement. The code originally passed the string containing the comma-separated values directly, which resulted in MySQL treating the entire string as a single value rather than a set of values.

The solution involved passing an array of references to each of the values in the 'lastnames' array, along with a string specifying the type of each value. By doing so, MySQL correctly recognized and bound each value individually. This allowed the IN operator to function as intended, resulting in the successful retrieval of the desired rows.

While this solution may not be the most elegant or succinct, it effectively addresses the issue and demonstrates the importance of correctly binding parameters when using prepared statements with the IN operator.

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