php - MySQL where 字母数字列的条件

Question

我的员工表有一个工作级别列，其中包含 1A、1B、1C、2A、2B 和 2C 等值。员工等级为 2C > 2B > 2A > 1C > 1B > 1A。

现在，如果我编写这样的查询：

SELECT *
FROM employee
WHERE work_level >= 1C

它会返回仅包含工作级别 1C、2A、2B、2C 的行吗？

如果没有，那我该怎么办？

Answer 1

是的，它将返回所需的行，但请记住在 where 子句中添加一个逗号：

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

Answer 2

尝试这样的事情：

假设您有一些work_levels 和 input 定义如下：

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';  

运行以下查询：

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'''
;

会导致：

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