Oracle - 在REGEX_COUNT函数的第一个参数中使用别名

Question

是否可以使用别名作为REGEXP_COUNT函数中的第一个参数，而不是实际的字段名称。比如我用下面的：

SELECT first_name ||' '|| last_name as fullname, 
     REGEXP_COUNT(fullname, 'o', 1, 'i') AS total 
FROM BROKERS 

我不断收到一个错误，让我觉得我会称呼其为一个场，而不是调用连锁的“全名”

Answer 1

为“无效的标识符”在评论中提到，你需要使用子查询：

SELECT REGEXP_COUNT(b.fullname, 'o', 1, 'i') AS total 
    FROM (SELECT first_name ||' '|| last_name as fullname 
      FROM BROKERS) b; 

或者你可以做串联的功能：

SELECT first_name ||' '|| last_name as fullname, 
     REGEXP_COUNT(first_name ||' '|| last_name, 'o', 1, 'i') AS total 
    FROM BROKERS 
GROUP BY first_name ||' '|| last_name; 

如果你要选择你还需要一个group by

SELECT b.fullname, 
     REGEXP_COUNT(b.fullname, 'o', 1, 'i') AS total 
    FROM (SELECT first_name ||' '|| last_name as fullname 
      FROM BROKERS) b 
    GROUP BY b.fullname;