MySQL在字母數字列的條件

Question

我的員工表有一個包含如1A，1B，1C，2A，2B，& 2C等值的工作級別的列。 員工等級爲2C> 2B> 2A> 1C> 1B> 1A。

現在，如果我寫這樣的查詢：

SELECT * 
FROM employee 
WHERE work_level >= 1C 

是重回僅含工作水平1C，2A，2B，2C行？

如果不是，那我該怎麼辦？

Answer 1

是的，它會返回所需的行，但千萬記得要倒逗號添加到where子句::

SELECT * FROM employee WHERE work_level >= '1C' 

Answer 2

嘗試是這樣的：

讓我們說你有一些work_level小號和輸入下文所定義：

set @work_level1 = '25C'; 
set @input_work_level1 = '1C'; 

set @work_level2 = '2C'; 
set @input_work_level2 = '15C'; 

set @work_level3 = '2A'; 
set @input_work_level3 = '1C'; 

set @work_level4 = '2C'; 
set @input_work_level4 = '15B'; 

運行以下查詢：

select 
(cast(left(@work_level1, length(@work_level1)-1) as unsigned) 
    >= 
    cast(left(@input_work_level1, length(@input_work_level1)-1) as unsigned) 
) 
and 
right(@work_level1, 1) <= right(@input_work_level1, 1) 
as '''25C'' >= ''1C''', 

(cast(left(@work_level2, length(@work_level2)-1) as unsigned) 
    >= 
    cast(left(@input_work_level2, length(@input_work_level2)-1) as unsigned) 
) 
and 
right(@work_level2, 1) <= right(@input_work_level2, 1) 
as '''2C'' >= ''15C''', 

(cast(left(@work_level3, length(@work_level3)-1) as unsigned) 
    >= 
    cast(left(@input_work_level3, length(@input_work_level3)-1) as unsigned) 
) 
and 
right(@work_level3, 1) <= right(@input_work_level3, 1) 
as '''2A'' >= ''1C''', 

(cast(left(@work_level4, length(@work_level4)-1) as unsigned) 
    >= 
    cast(left(@input_work_level4, length(@input_work_level4)-1) as unsigned) 
) 
and 
right(@work_level4, 1) <= right(@input_work_level4, 1) 
as '''2C'' >= ''15B''' 
; 

會導致：

+---------------+---------------+--------------+---------------+ 
| '25C' >= '1C' | '2C' >= '15C' | '2A' >= '1C' | '2C' >= '15B' | 
+---------------+---------------+--------------+---------------+ 
|    1 |    0 |   1 |    0 | 
+---------------+---------------+--------------+---------------+