Join two queries in mysql/php - php

Question

I need some help with this:
I'm doing a search with several parameters: Category, date(from), date(to)
Here's the code:
if (count($categorias) > 0) {
for ($i = 0; $i < count($categorias); $i++) {
if ($i == 0) {
$query = "WHERE id_subcategoria = " . $categorias[$i] . " ";
} else {
$query .= " OR id_subcategoria = " . $categorias[$i] . " ";
}
}
} else {
$query = "";
}
if (!$sql = $db->sql_query("SELECT * FROM actividades $query ORDER BY id DESC LIMIT " . $pageLimit . "," . PAGE_PER_NO)) {
message_die("DS", TRUE);
}
$total = $db->sql_numrows($sql);
if ($total != 0) {
while ($linha = $db->sql_fetchrow($sql)) {
$SqlEstado = $db->sql_query("SELECT * FROM tarifas WHERE id_actividade = " . $linha['id'] . " AND dia = '$data_min'");
First I get all the products that match the category and then I go to table "tarifas" to check if the product is available to be booked on that day.
So my question is: Can I do it all in one query? selecting the product and in case there's a rule in table "tarifas" fetch that rule.
If it's not clear enough please let me know so I can expose the problem in a different way, i'm really struggling with this.

Answer 1

Yes, you perform a JOIN on the id columns. If you want just those products that are in "tarifas" it will be an INNER JOIN, if you want the products even if they aren't in "tarifas" it will be "actividades LEFT JOIN tarifas ON ...".

Answer 2

Thanks for the help, user3038802!
Here's the code in case it helps anyone with the same problem:
if (!$sql = $db->sql_query("SELECT actividades.nome, actividades.id, actividades.dias, actividades.preco FROM actividades LEFT JOIN tarifas ON actividades.id = tarifas.id_actividade AND tarifas.dia = '$data_min' $query")) {
message_die("DS", TRUE);
}