没有空字符串和NULL的mysql不同值 [英] mysql distinct values without empty string and NULL

问题描述

如何在没有空字符串值和NULL值的情况下检索mysql不同值

How to retrieve mysql distinct values without empty string value and NULL value

SELECT 
DISTINCT CON.EMAILADDRESS AS 'E-MAIL'
FROM  STUDENT
INNER JOIN CONTACT CON ON STUDENT.CONTACT_ID = CON.ID
WHERE
(CON.EMAILADDRESS IS NOT NULL 
OR  CON.EMAILADDRESS !=' ');

但在输出中仍然收到空电子邮件.无法弄清楚我在做什么错.

But in output still getting empty e-mails too. Can't figure out what wrong I am doing.

推荐答案

试试这个:

SELECT 
DISTINCT CON.EMAILADDRESS AS 'E-MAIL'
FROM  STUDENT AST
INNER JOIN CONTACT CON ON AST.CONTACT_ID = CON.ID
WHERE length(trim(CON.EMAILADDRESS)) >0 and CON.EMAILADDRESS IS NOT NULL  

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