Why Do I Get a Syntax Error When Executing Multiple MySQL Queries in PHP?

Executing Multiple MySQL Queries in PHP: Syntax Pitfalls and a Better Approach

In an attempt to execute multiple MySQL queries within a single PHP script, users may encounter a recurring syntax error. This article delves into the root cause of this error and provides a robust solution to avoid it.

The code snippet causing the syntax error appears as follows:

<code class="php">$sql = "CREATE TEMPORARY TABLE tmp SELECT * FROM event_categoriesBU WHERE id = 1;
UPDATE tmp SET id=100 WHERE id = 1;
INSERT INTO event_categoriesBU SELECT * FROM tmp WHERE id = 100;";</code>

The error message encountered suggests an incorrect syntax near the concatenation of multiple queries within the $sql variable. To resolve this, it's crucial to separate the queries instead of chaining them together.

A better approach involves iterating through each query individually, ensuring the successful execution of each step before proceeding to the next. This can be achieved using the following code:

<code class="php">$queries = [
  "CREATE TEMPORARY TABLE tmp SELECT * FROM event_categoriesBU WHERE id = 1",
  "UPDATE tmp SET id=100 WHERE id = 1",
  "INSERT INTO event_categoriesBU SELECT * FROM tmp WHERE id = 100"
];

foreach ($queries as $query) {
  $stmt = $conn->prepare($query);
  $stmt->execute();
}</code>

By adopting this approach, you ensure that each query is executed independently, mitigating the risk of compound errors. Additionally, consider enabling exceptions to halt the process in case of any failed queries, preventing uncontrolled execution.

It's also worth considering a switch to PDO (PHP Data Objects) as it offers greater flexibility and adaptability in database interactions.

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