sql server自定义排序（还有mysql）

select * from t_orderby 
where c2='4' 
union all 
select * from t_orderby 
where c2='1' 
union all 
select * from t_orderby 
where c2='2'

select * from t_orderby 
order by charindex(c2,'4,1,2') 

select * from t_orderby 
order by case 
         when c2='4' then 1 
         when c2='1' then 2 
         when c2='2' then 3 
         end,c1 desc

select * from t_orderby 
order by case 
         when c2='4' then 1 
         else 1+rand() 
         end

select * from t_orderby 
order by newid()

select top 1 * from t_orderby 
order by newid()

select * from t_orderby 
order by left(c3,1),ASCII(substring(c3,2,1))

问题描述
 

大家都知道, MySQL 中按某字段升序排列的 SQL 为 (以 id 为例, 下同):

SELECT * FROM `MyTable` 
WHERE `id` IN (1, 7, 3, 5) 
ORDER BY `id` ASC
降序排列的 SQL 为:

SELECT * FROM `MyTable` 
WHERE `id` IN (1, 7, 3, 5) 
ORDER BY `id` DESC
有时以上排序并不能满足我们的需求. 例如, 我们想要按 id 以 5, 3, 7, 1 的顺序排列, 该如何实现. 这也是很多国内外同行经常遇到的问题之一.

下面我们给出按表中某字段, 以我们想要的列表方式排序的解决方案.

解决方案
　　用"按字段排序" (ORDER BY FIELD).

语法
ORDER BY FIELD(`id`, 5, 3, 7, 1)
要注意的是, FIELD 后面是没有空格的.

因此, 完整的 SQL 为:

SELECT * FROM `MyTable` 
WHERE `id` IN (1, 7, 3, 5) 
ORDER BY FIELD(`id`, 5, 3, 7, 1)
常见应用
SELECT * FROM `MyTable` 
WHERE `name` IN ('张三', '李四', '王五', '孙六') 
ORDER BY FIELD(`name`, '李四', '孙六', '张三', '王五')