在 UNION 查询中结合 ORDER BY

Question

如何在 UNION 查询中组合 ORDER BY？

我试过了，但出错了：

SELECT country.country_name AS res
FROM   countries AS country
WHERE (lower (country.country_name) LIKE '%".$_POST['query']."%')
ORDER BY country.lang = '".$_POST['lang']."'
UNION
    SELECT  sec.loc AS res
    FROM    itin_secs AS sec
    WHERE   sec.loc LIKE '%".$_POST['query']."%'

Answer 1

我会推荐：

SELECT res
FROM (SELECT c.country_name as res, 1 as priority, c.lang
      FROM countries AS c
      WHERE lower(c.country_name) LIKE '%".$_POST['query']."%')
      UNION ALL  -- recommended instead of `UNION`
      SELECT  sec.loc Ares
      FROM itin_secs as sec, 2, NULL
      WHERE sec.loc LIKE '%".$_POST['query']."%'
    ) x
ORDER BY priority, lang = '".$_POST['lang']."';

这个查询对最终排序非常明确。它还使用UNION ALL，因此查询不会产生删除重复项的开销。

作为次要问题（我的意思是，原始查询不起作用），您应该参数化查询。你真的应该从编写参数化查询开始，所以它们对于你想做的任何事情都是很自然的。