MySQL類型轉換 使用CAST將varchar轉換成int類型排序

mysql為我們提供了兩個類型轉換函數：CAST和CONVERT，現成的東西我們怎能放過？

BINARY[(N)]
CHAR[(N)]
DATE
DATETIME
DECIMAL
SIGNED [INTEGER]
TIME
UNSIGNED [INTEGER]

 

例子：

--使用CAST將varchar轉換成int類型排序
select server_id from cardserver where game_id = 1 order by CAST(server_id as SIGNED) desc limit 10;

--使用CONVERT將varchar轉換成int類型排序
select server_id from cardserver where game_id = 1 order by CONVERT(server_id,SIGNED) desc limit 10