我可以按IN值订购吗？

Question

我可以按IN查询​​的值排序吗？

以下默认为"订购item_id最低优先"但我实际上希望排序为输入...这可能吗？

例如

select item_id, item_title, item_source from items where item_id IN ('1676','1559','1672')

我想回来:

item_id     item_title    item_source
-------     ----------    -----------
1676        item_a        source_a
1559        item_f        source_f
1672        item_c        source_c

Answer 1

你可以JOIN在IN谓词中使用这样的值:

SELECT 
  i.item_id,
  i.item_title
  i.item_source
FROM items i
INNER JOIN
(
   SELECT 0 sortid, 1676 id
   UNION ALL
   SELECT 1,        1559 
   UNION ALL
   SELECT 2,        1672
) t ON i.item_id = t.id
ORDER BY t.sortid

SQL小提琴演示

Answer 2

您需要一个自定义ORDER BY CASE来对每个可能的值应用排序等级.显然,随着集合的大小增加,这变得困难.

select
  item_id, 
  item_title, 
  item_source 
from items
where item_id IN ('1676','1559','1672')
/* Custom ORDER BY applies lower order numbers to the lowest value, etc... */
ORDER BY 
  CASE 
    WHEN item_id = 1676 THEN 0
    WHEN item_id = 1559 THEN 1
    WHEN item_id = 1672 THEN 2
    /* If you had others (which you don't because they're limited by the IN() clause, include an ELSE */
    ELSE 99
  END,
  /* Then complete the ORDER BY with other cols to order on as needed... */
  item_source

Answer 3

如果您事先已经知道 ID，则可以考虑使用FIND_IN_SET或函数来组织结果。FIELD

SELECT 
    item_id,
    item_title,
    item_source
FROM items
WHERE item_id IN ('1676','1559','1672')
ORDER BY FIELD(item_id, '1676', '1559', '1672')

或者

ORDER BY FIND_IN_SET(item_id, '1676,1559,1672')

当然，缺点是您需要指定两次 ID。不过，我认为几乎任何性能合理的解决方案都会这样做。解决这个问题的唯一方法是有一个排序顺序字段或类似的东西。