如何UPPER子查询？(how to UPPER subquery?)

如何UPPER子查询？(how to UPPER subquery?)

Oracle SQL Developer：

我需要比较upcase子查询输出结果与字符串，但下面的代码不起作用 - 缺少表达式

SELECT UPPER（从'DUAL中选择'abcd'来自DUAL）

但同时我可以执行此操作

从DUAL中选择UPPER（'abcd'）

请告知如何避免此问题并在UPPER中使用子查询。

Oracle SQL Developer:

I need to compare upcase subquery output result with a string, but the code below does not work - missing expression

SELECT UPPER(SELECT 'abcd' FROM DUAL) FROM DUAL

but at the same time I can execute this

SELECT UPPER('abcd') FROM DUAL

Please advise how to avoid the problem and use subquery within UPPER.

最满意答案

尝试重新调整查询以允许别名子查询中的值。

SELECT UPPER(t.val) AS val FROM (SELECT 'abcd' AS val FROM DUAL) t;

Try rephrasing your query to allow aliasing the value inside the subquery.

SELECT UPPER(t.val) AS val FROM (SELECT 'abcd' AS val FROM DUAL) t;