MYSQL按秒表排序 - MYSQL order by second table

MYSQL order by second table

本文关键字：排序 MYSQL | 更新日期: 2023-09-27

我有一个名为properties的表，我想获取该表中与"hold=1"匹配的所有记录，但另一个表包含不同语言的属性名称。我需要获取英语，或者如果不存在，语言标记为默认

表格属性：

pid     hold

属性_翻译：

pid     lang_id     pname     description     isDefault

我通常使用联合获取语言

(select pname from property_translations where lang_id='en' and pid=$pid)
union
(select pname from property_translations where isDefault='Yes' and pid=$pid)
limit 1

SELECT p.pid, t.pname FROM properties p LEFT OUTER JOIN translations t ON p.pid = t.pid
    WHERE p.hold=1 AND t.isDefault='Yes' AND NOT EXISTS
    ( SELECT * FROM translations ti WHERE ti.pid = p.pid AND ti.lang_id='en')
    UNION SELECT p.pid, t.pname FROM properties p 
    LEFT OUTER JOIN translations t ON p.pid = t.pid
    WHERE p.hold=1 AND t.lang_id='en';

尝试：

   SELECT pt.pname
     FROM property_translations AS pt
LEFT JOIN properties AS p ON p.pid = pt.pid
    WHERE pt.pid = $pid
      AND p.hold = 1
      AND pt.lang_id='en'
      AND isDefault='Yes'

如果您的select为您提供了所需的结果，并且您只想通过hold=1对其进行筛选，那么您可以简单地加入第一个表：

(select pname from property_translations t
              join properties p on (t.pid=p.pid and p.hold = 1)
              where lang_id='en' and pid=$pid)
union
(select pname from property_translations t
              join properties p on (t.pid=p.pid and p.hold = 1)
              where isDefault='Yes' and pid=$pid
              and not exists (select 1 from property_translations t2
                              where t2.pid=t.pid and t2.lang_id='en' and t2.isDefault='Yes'))

请注意，我不是在检查您原始select的有效性，只是展示如何根据第二张表添加支票。

SELECT p.pid pid, pname
from properties p
JOIN (SELECT t1.pid tpid, IFNULL(t2.pname, t1.pname) pname
      FROM translations t1
      LEFT OUTER JOIN translations t2
      ON t1.pid = t2.pid
      AND t2.lang_id = 'en'
      WHERE t1.isDefault = 'Yes') t
ON p.pid = t.pid
WHERE p.hold = 1