Mysql 如何在order by语句中按DESC放置字符串值

我用mySQL写了一个程序

IN `para`  varchar(4)
BEGIN
    #Routine body goes here...

if (para = 'asc') THEN

SELECT officeCode, city, country
from offices
ORDER BY country ;

ELSE

SELECT officeCode, city, country
from offices
ORDER BY country DESC;


END if;
END

这段代码还可以，但我想知道是否有其他方法可以缩短代码，比如这样（当调用过程时，para是参数）：

---

如果您选择的脚本语言在您的解决方案中有效，您可以非常轻松地基于

para

使用您选择的任何脚本语言动态生成查询文本。

您可以非常轻松地基于

para

使用您选择的任何脚本语言动态生成查询文本，如果这在您的解决方案中起作用。

下面是一个技巧，您可以使用

案例

表达式：

SELECT officeCode,
       city,
       country
FROM offices
ORDER BY CASE WHEN para = 'asc'  THEN Country ELSE '1' END ASC,
         CASE WHEN para != 'asc' THEN Country ELSE '1' END DESC;

---

下面是一个技巧，可用于

案例

表达式：

SELECT officeCode,
       city,
       country
FROM offices
ORDER BY CASE WHEN para = 'asc'  THEN Country ELSE '1' END ASC,
         CASE WHEN para != 'asc' THEN Country ELSE '1' END DESC;

---

你有两个选择。一种是通过摆弄命令：

SELECT officeCode, city, country
FROM offices
ORDER BY (CASE WHEN para = 'asc' THEN country END),
         country DESC;  -- you could use a `case` here but it is not necessary

或者，您可以使用准备好的语句：

set @sql = '
SELECT officeCode, city, country
FROM offices
ORDER BY para [dir]';

set @sql = replace(@sql, '[dir]', (case when para = 'asc' then 'asc' else 'desc' end));

prepare q from @sql;
execute q;

---

动态SQL的优点是您希望查询将使用索引。

您有两个选择。一种是通过摆弄命令：

SELECT officeCode, city, country
FROM offices
ORDER BY (CASE WHEN para = 'asc' THEN country END),
         country DESC;  -- you could use a `case` here but it is not necessary

或者，您可以使用准备好的语句：

set @sql = '
SELECT officeCode, city, country
FROM offices
ORDER BY para [dir]';

set @sql = replace(@sql, '[dir]', (case when para = 'asc' then 'asc' else 'desc' end));

prepare q from @sql;
execute q;

动态SQL的优点是您希望查询将使用索引