如何在Oracle sql中过滤空值

Question

我想过滤 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。我该怎么办？

Answer 1

NULL是一个非价值的州，因此您无法在其上使用普通运算符。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;

只是看到你不需要所有这些子查询

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