MySQL group_concat()按case语句值排序

Question

在MySQL group_concat()子句中,我正在尝试对case语句的结果值进行排序.以下查询配置正确things.name排序,但未在同一上下文中排序"非美国"或"未知"值.

SELECT 
  things.id
  ,group_concat(DISTINCT 
    CASE
    WHEN things.name <> 'United States' THEN 'Non-US'
    WHEN things.name IS NULL THEN 'Unknown'
    ELSE things.name
    END
  ORDER BY name SEPARATOR ', ')
FROM things
GROUP BY things.id

我想做这样的事情,但它不起作用:

SELECT 
  things.id
  ,group_concat(DISTINCT 
    (CASE
    WHEN things.name <> 'United States' THEN 'Non-US'
    WHEN things.name IS NULL THEN 'Unknown'
    ELSE things.name
    END) AS new_name
  ORDER BY new_name SEPARATOR ', ')
FROM things
GROUP BY things.id

有没有办法按"new_name"排序而不使用子查询/嵌套查询？

Answer 1

您可以通过按列位置而不是列名称进行排序来完成此操作.

对于你的情况ORDER BY 1应该工作.

SELECT 
  things.id
  ,group_concat(DISTINCT 
    CASE
    WHEN things.name <> 'United States' THEN 'Non-US'
    WHEN things.name IS NULL THEN 'Unknown'
    ELSE things.name
    END
  ORDER BY 1 SEPARATOR ', ')
FROM things
GROUP BY things.id