将NVL用于多个列 - Oracle SQL

Good morning my beloved sql wizards and sorcerers,

早上好，我亲爱的sql巫师和巫师，

I am wanting to substitute on 3 columns of data across 3 tables. Currently I am using the NVL function, however that is restricted to two columns.

我想要在3个表中替换3列数据。目前我正在使用NVL功能，但是这仅限于两列。

See below for an example:

请参阅下面的示例：

    SELECT ccc.case_id,
           NVL (ccvl.descr, ccc.char)) char_val

               FROM case_char ccc, char_value ccvl, lookup_value lval1
              WHERE   
                    ccvl.descr(+) = ccc.value
                    AND ccc.value = lval1.descr (+)
                    AND ccc.case_id IN ('123'))



     case_char table
     case_id|char |value
       123  |email| work_email
       124  |issue| tim_ 



     char_value table
     char  | descr
work_email | complaint mail
    tim_   | timeliness


    lookup_value table
    descr  | descrlong
 work_email| xxx@blah.com

Essentially what I am trying to do is if there exists a match for case_char.value with lookup_value.descr then display it, if not, then if there exists a match with case_char.value and char_value.char then display it.

基本上我要做的是，如果case_char.value与lookup_value.descr存在匹配，则显示它，否则显示它，如果存在与case_char.value和char_value.char的匹配则显示它。

I am just trying to return the description for 'issue'from the char_value table, but for 'email' I want to return the descrlong from the lookup_value table (all under the same alias 'char_val').

我只是想从char_value表中返回'issue'的描述，但对于'email'，我想从lookup_value表中返回descrlong（所有这些都在同一个别名'char_val'下）。

So my question is, how do I achieve this keeping in mind that I want them to appear under the same alias.

所以我的问题是，如何实现这一点，请记住，我希望它们出现在相同的别名下。

Let me know if you require any further information.

如果您需要任何进一步的信息，请告诉我。

Thanks guys

多谢你们

2 个解决方案

#1

You could nest NVL:

你可以嵌套NVL：

 NVL(a, NVL(b, NVL(c, d))

But even better, use the SQL-standard COALESCE, which does take multiple arguments and also works on non-Oracle systems:

但更好的是，使用SQL标准COALESCE，它确实采用多个参数，也适用于非Oracle系统：

COALESCE(a, b, c, d)

#2

How about using COALESCE:

如何使用COALESCE：

COALESCE(ccvl.descr, ccc.char)

#1