oracle - Oracle sql中如何过滤空值

Question

我要过滤COMMENTS属性为空的记录

我试过了

SELECT TABLE_NAME, COMMENTS FROM 
    (SELECT TABLE_NAME, COMMENTS FROM (select * FROM user_tab_comments))
    WHERE COMMENTS != null;

但它没有返回正确的输出。我该怎么做？

Answer 1

NULL 是状态而不是值，因此您不能对其使用普通运算符。请改用 IS NULL 或 IS NOT NULL。

SELECT TABLE_NAME, COMMENTS 
  FROM (SELECT TABLE_NAME, COMMENTS FROM (select * FROM user_tab_comments))
    WHERE COMMENTS IS NOT NULL;

刚看到您不需要所有这些子查询

SELECT TABLE_NAME, COMMENTS 
  FROM user_tab_comments 
 WHERE COMMENTS IS NOT NULL;