是否有可能在SQL中的SELECT中合併？

Question

比方說，我想要從一個叫messages表100分的記錄，我想獲得它們的方式如下：

1st message 
100th message 
2nd message 
99th message 
3rd message 
98th message 
(...) 

有沒有辦法做到這一點有效？什麼是適當的查詢？ 或者我應該查詢選擇前50，查詢選擇最後50，然後合併結果？

Answer 1

嘗試，如果你的ID是數字的序列：

首先

SET @half = (SELECT MAX(id) FROM messages)/2; 

然後

SELECT * FROM `messages` ORDER BY (IF(id<@half,@half*2-id,id-1)) DESC,id ASC; 

Answer 2

的一點是要創建兩個虛擬列 「serie_order」（變體）和「系列「（常量），你將使用你的兩部分數據（你將不得不將數據分成兩部分）。

SELECT * FROM (
    SELECT 1 as serie, message_id AS serie_order , * FROM 
    (SELECT message_id FROM messages) as part_up 
UNION 
    SELECT 2 as serie, 101-message_id as serie_order, * FROM 
    (SELECT message_id FROM messages) as part_down 
) AS world 

ORDER BY serie_order ASC, serie ASC 
LIMIT 100 

Answer 3

set @rank:=0; 

select id from 
(select id, @rank:=(coalesce(@rank, 0)+1) as new_order 
from a_table 
order by some_column limit 100) as ordering 
order by if (new_order<=50, new_order-1, abs(100-new_order)) asc;