php - IF NOT EXISTS then INSERT else show message 不工作

Question

我有一个包含“引用”的表，其想法是如果引用已经存在，则不会插入。如果它不存在，那么它会插入。但是这段代码不会以任何一种方式插入。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(); 

Answer 1

制作 column as Unique .然后 Insert 并且不必担心该行的存在。如果它已经存在，则返回 FALSE。