sql - SQL查询用另一个替换表的记录

Question

以下代码会产生错误：

select lastname, firstname, workphone, homephone 
from members if (workphone is null) then workphone = homephone;

我正在尝试从名为 的表中选择lastnames和firstnames您的电话号码members。如果成员的workphone is null我需要将其替换为homephone.

如果需要，我将非常乐意澄清。

Answer 1

您可以使用该COALESCE函数，它返回给定的第一个非空参数：

SELECT lastname, firstname, homephone, COALESCE(workphone, homephone) AS workphone
FROM   members

Answer 2

select lastname, firstname, 
case when (workphone is null) then homephone  else workphone end as workphone 
, homephone 
from members;