SQL中的控制流问题

Question

In the php script, there is a variable named $partners_location .

In the SQL there is a column named plocation .

What I want to do is first check if there is any value in the column plocation which matches the value of $partners_location .

If it does match then I want to go ahead and create a new table, from php script itself.

For this type of situation I know what we need is If else , but I don't know how to use it here

This is what I have been trying, by the way I am using PDO.

$dsn= "mysql:dbname=mydatabase";
$name= "root";
$password="****";
$conn = new PDO ($dsn, $name, $password);

...

if($CON = $conn->prepare("SELECT FROM CIDB WHERE plocation='$partners_location'");
    $CON->execute();)
{
 $tbl=$conn->prepare("CREATE TABLE chat (id INT NOT NULL);
}
else
{
$tbl=$conn->prepare("CREATE TABLE xyz (id INT NOT NULL);
}

I don't think that these if else statements are going to work.

Can someone suggest me something that would work?

Answer 1

$CON->execute() will return true even if the query is successful but zero rows are returned.
Use COUNT() to check if rows exist.
Like this:

$CON = $conn->prepare("SELECT COUNT(*) as cnt FROM CIDB WHERE plocation = '$partners_location'");
$CON->execute();
$row  = $CON-> fetch();
if($row[0] != '0' )
    $tbl=$conn->prepare("CREATE TABLE chat (id INT NOT NULL)");
else
    $tbl=$conn->prepare("CREATE TABLE xyz (id INT NOT NULL)");

Answer 2

Try this:

$CON = $conn->prepare("SELECT COUNT(*) as cnt FROM CIDB WHERE plocation = '$partners_location'");
$CON->execute();
$row  = $CON-> fetch();
if($row[0] != '0' )
{
    $tbl=$conn->prepare("CREATE TABLE chat (id INT NOT NULL)");
}
else
{
    $tbl=$conn->prepare("CREATE TABLE xyz (id INT NOT NULL)");
}

You missed ")