SQL DB2：如何在 DB2 中连接空字符串？

Question

提问by adrift

I have to concatenate 2 columns (ex. FIRSTANME and LASTNAME).
I do it this way:

我必须连接 2 列（例如 FIRSTANME 和 LASTNAME）。
我这样做：

FIRSTNAME || ' ' || LASTNAME`.

If one of them is null, but the other one is not null, I get null as concatenation result.
And I want following behavior

如果其中一个为空，而另一个不为空，则我将获得空作为连接结果。
我想要以下行为

FIRSTNAME = null and LASTNAME = "Smith" ==> 
  FIRSTANME || ' ' || LASTNAME == ' Smith'.

How to solve this in DB2?

如何在 DB2 中解决这个问题？

Answer 1

Use coalesce

用 coalesce

...
CONCAT( COALESCE(firstname,'') , COALESCE(lastname,'') )

Or using the ||concat operator

或者使用||concat 运算符

...
COALESCE(firstname,'') || COALESCE(lastname,'')

Note that IBM recomments using the keyword concatand not the ||operator.

请注意，IBM 建议使用关键字concat而不是||运算符。