我有一个表'引用'在它，这个想法是，如果一个引用已经存在，那么它不会插入。如果它不存在，它就会插入。但是这段代码不能任意插入。请协助。
$dbconn = pg_connect("host=127.0.0.1 dbname=XX user=XX password=XX") or die('Could not connect: ' . pg_last_error());
$query = "IF NOT EXISTS (SELECT reference FROM card WHERE reference = '$reference')
INSERT INTO staff (reference, first_name, last_name, address1, address2, address3, address4)
VALUES ('$reference', '$first_name', '$last_name', '$address1', '$address2', '$address3', '$address4')";
$result = pg_query($query);
if (!$result)
{
echo "Customer update failed!! This ID might already be registered with us. Please go back and check the spelling of your email address.<br><br><input type='"button'" value='"Go Back'" onClick='"history.go(-1);return true;'">";
die;
} else
{
echo "Customer update successful; ";
}
pg_close();
设置列为Unique。然后插入，不用担心该行是否存在。如果已经存在，则返回FALSE。
try{
$db = new PDO("pgsql:dbname=yourdbname charset=utf8","username","password");
$query=$db->prepare("
insert into staff (
reference, first_name, last_name,
address1, address2, address3, address4
)
select * from (
select ? as reference, ?, ?, ?, ?, ?, ?
) as _
where reference not in (select reference from staff)
");
$insert = $query->execute(array(
$reference, $first_name, $last_name,
$address1, $address2, $address3, $address4
));
if ($insert->rowCount() == 0) {
echo "ERROR: Customer already exists!";
} else {
echo "Customer account creation successful!";
}
} catch(PDOException $e) {
echo "Error: ".$e;
}