Why is the SELECT query used in this code if the UPDATE condition determines whether to update or not?

The SELECT query is used in this code to check if the record meets the conditions for updating before actually performing the update operation. This is a common practice to ensure that unnecessary update queries are not executed, which can improve performance and reduce the risk of unintended updates. To solve this issue, you can combine the SELECT and UPDATE queries within a single transaction to ensure atomicity and consistency. 

<?php
// Establish a database connection
$pdo = new PDO("mysql:host=localhost;dbname=test_db", "username", "password");

// Begin a transaction
$pdo->beginTransaction();

// Select query to check if the record meets the conditions for updating
$stmt = $pdo->prepare("SELECT * FROM table_name WHERE condition = :condition");
$stmt->bindParam(':condition', $condition_value);
$stmt->execute();
$row = $stmt->fetch();

if ($row) {
    // Update query within the same transaction
    $updateStmt = $pdo->prepare("UPDATE table_name SET column_name = :new_value WHERE condition = :condition");
    $updateStmt->bindParam(':new_value', $new_value);
    $updateStmt->bindParam(':condition', $condition_value);
    $updateStmt->execute();

    // Commit the transaction if the update is successful
    $pdo->commit();
} else {
    // Rollback the transaction if the record does not meet the conditions for updating
    $pdo->rollBack();
}

// Close the database connection
$pdo = null;
?>

Keywords

SELECT query UPDATE condition PHP code database manipulation SQL syntax

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