PostgreSQL行排序为NULL值，最后为空字符串

Question

我使用了以下SQL，它工作正常，但我还要对空字符串进行排序。请给我指导。

SELECT id, first_name, last_name 
FROM users
ORDER BY first_name DESC NULLS LAST
limit 10;

Answer 1

使用一些conditional functions，例如

ORDER BY NULLIF(first_name, '') DESC NULLS LAST

Answer 2

ORDER BY IF(first_name = '' OR first_name IS NULL,1,0), first_name;