对别名执行 mySQL 搜索

Question

搜索别名的正确方法是什么？在下面的代码中，我创建了一个名为 (USER) 的别名，在此列中，我收集了 (DE) 和 (PARA) 列中的所有值。(SELECT *, de as user FROM mensagens WHERE user = '1' GROUP BY projeto ORDER BY data DESC)    UNION(SELECT *, para as user  FROM mensagens WHERE user = '1' GROUP BY projeto ORDER BY data DESC)SQL在线：http ://sqlfiddle.com/#!9/d506b7/2

Answer 1

你可以做

select * from 

(

  SELECT *, de as user FROM mensagens

  UNION

  SELECT *, para FROM mensagens

) tmp

where user = 1

GROUP BY projeto 

ORDER BY data DESC

SQLFiddle 演示

或者更简单：

SELECT * 

FROM mensagens

WHERE 1 in (de, para)

GROUP BY projeto 

ORDER BY data DESC