How can i change this select sql statement into another select sql? - php

Question

I have code the below code works fine but i want to have one sql statement instead of few in this code so when i try to change into one i get an error.
$eventID = $_GET['id'];
$sql = "SELECT * FROM te_events where eventID='$eventID'";
$result = $conn->query($sql);
while($row = $result->fetch_assoc())
{
$eventTitle = $row['eventTitle'];
$eventDescription = $row['eventDescription'];
$eventStartDate = $row['eventStartDate'];
$eventEndDate = $row['eventEndDate'];
$eventPrice = $row['eventPrice'];
$venueID = $row['venueID'];
$catID = $row['catID'];
$sql2 = "SELECT * FROM te_venue where venueID='$venueID'";
$result2 = $conn->query($sql2);
while($row2 = $result2->fetch_assoc())
{
$venueName = $row2['venueName'];
}
$sql3 = "SELECT * FROM te_category where catID='$catID'";
$result3 = $conn->query($sql3);
while($row3 = $result3->fetch_assoc())
{
$catName = $row3['catDesc'];
}
}
?>
I changed the code into this but it seems it is not working.
<?php
$eventID = $_GET['id'];
$sql = "SELECT * FROM te_events where eventID='$eventID' AND where venueID='$venueID' From te_venue AND where catID='$catID' From te_category";
$queryresult = mysqli_query($conn, $sql) or die(mysqli_error($conn));
while ($row = mysqli_fetch_array($queryresult)) {
$eventTitle = $row['eventTitle'];
$eventDescription = $row['eventDescription'];
$eventStartDate = $row['eventStartDate'];
$eventEndDate = $row['eventEndDate'];
$eventPrice = $row['eventPrice'];
$venueID = $row['venueID'];
$catID = $row['catID'];
$catName = $row['catDesc'];
$venueName = $row['venueName'];
}
?>
And i get this error.
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'where venueID='' From te_venue AND where catID='' From te_category' at line 1

Answer 1

Yes, you can do that. But in order to get the fields that you want from all three tables, you have to join them together.
Look at this article on W3S: http://www.w3schools.com/sql/sql_join.asp. It explains SQL JOIN syntax and the basic theory behind.
If you just joined venue and event Your select statement looks like:
SELECT * FROM te_event
JOIN te_venue
ON te_vendue.venueID = te_event.venueID
WHERE te_event.eventID = $eventID
The category table is similar.
Note: In general, use of SELECT * is discouraged. Your should list the fields that you want returned from the tables. ie. SELECT te_eventID, te_venueID

Answer 2

You could use joins as below;
SELECT * FROM te_events
JOIN te_venue ON te_events.venueID = te_venue.venueID
JOIN te_category ON te_events.catID = te_category.catID
WHERE eventID = :EventID
As mentioned you should also use PDO's:
define( "DB_DSN", "mysql:host=localhost;dbname=foo");
define( "DB_USERNAME", "root");
define( "DB_PASSWORD", "password" );
// define sql
$sSQL = "SELECT * FROM te_events
JOIN te_venue ON te_events.venueID = te_venue.venueID
JOIN te_category ON te_events.catID = te_category.catID
WHERE eventID = :EventID";
// create an instance of the connection
$conn = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
// prepare
$st = $conn->prepare( $sSQL );
// securely bind any user input in the query
$st->bindValue(":EventID", $iEventID, PDO::PARAM_INT);
// execute the connection
$st->execute()
$aResults = array();
// loop over results and store in aResults
while($row = $st->fetch()){
$aResults[] = $row;
}
// output data
foreach($aResults as $aResult){
echo "title: ".$aResult['eventTitle'];
}
You should always avoid using select *. Especially when your doing joins. Ensure you request only what you need and alias if you require duplicate column names