Can I use a SELECT inside the IF?

Question

It occurred to me to try to do this action, but it seems to give error. It is possible?

//EVITANDO DUPLICIDADE
if ($legenda > "0") {
    SELECT legenda FROM aula_upload_arquivo WHERE legenda = $legenda;
    echo 'Existe esse arquivo';
} else {
    echo 'Não existe o arquivo';
}

Answer 1

You can, but not this way. In order to use SQL you must use some function for this, such as mysqli_query or equivalent.

That way, it would be like doing:

if ($legenda > 0) {
   $result = mysqli_query($con, "SELECT legenda FROM aula_upload_arquivo WHERE legenda = '$legenda'");
   // ...
} else {
   // ...
}

There is nothing wrong with running a query inside a if. If that’s already what you’re doing, then mention the exact error that occurs.

Answer 2

PROBLEM SOLVED:

01) It was not necessary to do this action with SELECT within IF. 02) Much easier, it was to transform one of the fields into UNIQUE 03) So that the data is always exclusive, the information was inserted in the field, using the user’s name and his ID, along with any noun.

Answer 3

$conn = mysqli_connect(DB_HOST, DB_USER, DB_PASS, DB_NAME);
$result = mysqli_query($conn, "SELECT * FROM table WHERE dado='$dado'");
if(mysqli_num_rows($result) > 0){
echo "Este Dado já existe";
exit();
} else {
 if(mysqli_query($conn, "INSERT INTO table (dado) VALUES ('$dado')");
 echo "Dados inseridos com sucesso";
}