如何将MySQLi返回对象用作新SQL查询的表

Question

I don't understand how we can use the results that is a table from a SELECT query for new queries. Let's say we join two tables using INNER JOIN and we get a mysqli return object holding the rows of the joined table as an array. But how can I use this for new queries. I tried doing it by using the result object $result as a mysql table but it doesn't work, neither does doing $result->fetch_all() make it into a table.

I have a form that takes in $_GET['winery_name'] and $_GET['wine_type'] that are both strings in winery and wine_type tables. I need to go from their string value to their id values that are their primary keys and serve as foreign keys in wine table.

Depending on the winery_name and wine_type, I have to filter out the wine table and post filtered results. My approach so far doesn't work and I don't understand how to make it work using join tables. Here's what I have so far:

  <?php
if (count($_GET) > 0){

$sql = "SELECT * FROM winery where winery_name='".$_GET['winery_name']."'";
echo "Finished 1";
$result = $db->query($sql);
echo "Finished 2";

$row = $result->fetch_object();
$wineryid = $row -> winery_id;
echo "Winery id is ".$wineryid;


$sql = "SELECT * FROM wine where wine.winery_id =".$wineryid;
$result1 = $db->query($sql);
echo "Finished 4";


$sql = "SELECT * FROM wine_type where wine_type='".$_GET['wine_type']."'";
echo "Finished 5";
$result = $db->query($sql);
echo "Finished 6";

$row = $result->fetch_object();
$winetypeid = $row -> wine_type_id;
echo "Wine type id is ".$winetypeid;
//code stops working here
$sql = "SELECT * FROM ".$result1." WHERE wine_type =".$winetypeid;
echo "Finished 8";
$result = $db->query($sql);
echo "Finished 9";

while($row = $result1->fetch_object()){

    echo $row->wine_name;
}

}
?>

Here's the ER diagram:

Again, I am trying to go from winery_name(string) to winery_id(int) in winery and wine_type(string) to wine_type_id(int) in wine_type . Then using the int values to filter out wines from wine table. Also wine_type is an int value in in wine but string in wine_type .

If there is a way to make this statement work please let me know:

$sql = "SELECT * FROM ".$result1." WHERE wine_type =".$winetypeid;

wine:

winery

wine_type

Answer 1

You cannot do this on the web server. Once the Query results have been transferred from the database to the client Server, the database releases all references to the Query results.

This can be done with a nested select Statement:

SELECT a, b FROM (
    SELECT a, b FROM c JOIN d ON a =e
)