php - 更新查询 MySQL PDO 时的情况

Question

如何使用 CASE WHEN 在 MySQL 和 PDO 中运行更新查询。以下查询将 CASE 列更新为 0。

$query= "Update payments SET 
                            total = :total,
                            paid = CASE
                                      WHEN paid > :new THEN paid = :new
                                   ELSE paid
                                   END,
                            due = CASE
                                     WHEN paid < :new THEN due = :new - paid
                                  ELSE due
                                  END
                             WHERE id = :id ";

                        $update= $db->prepare($query);

                        $update->bindparam(':total',$new);
                        $update->bindparam(':new',$new);
                        $update->bindparam(':id',$id);
                        $update->execute();

Answer 1

不要尝试在 CASE WHEN 语句中将值分配给您的列，因为您已经在这样做了。
CASE WHEN 将评估满足条件的值。
试试这段代码

UPDATE payments SET 
 total = :total,
 paid = (CASE WHEN paid > :new THEN :new ELSE paid END),
 due = (CASE WHEN paid < :new THEN (:new - paid) ELSE due END)
 WHERE id = :id 

我删除了 case 语句中已付和到期列的分配。