仅当记录不存在时插入数据
问题描述：
只有当给定 CatalogID 的记录不存在时，我才想要在表格中插入数据。
I want to insert data in a table only if the record with a given CatalogID does not exist.
$userId = $_POST['userId'];
$catalogID = $_POST['catalogID'];
$content_AddedTime = $_POST['content_AddedTime'];
$query = ("INSERT INTO LibraryMaster (UserID,CatalogID,ContentAddedDateTime)
VALUES ('$userId','$catalogID','$content_AddedTime')");
mysql_query($query,$con);
printf("Records inserted: %d\n", mysql_affected_rows());
echo($user_Name)
答
UNIQUE 索引在 CatalogID 。