转换行与列在MySQL

Question

 
------------------------------------------------------------ 
courseid|course |coursedesc        | 
------------------------------------------------------------ 
1  | BSIT  | Bachelor of science in info tech  | 
2  | BSCS  | Bachelor of science in comp sci  | 
3  | BSHRM | Bachelor of science in hotel & res | 

我想将其转换为这样的事情动态

 
--------------------------------- 
|course1 | course2 | course3 | 
--------------------------------- 
BSIT  | BSCS  | BSCS  | 

我有这样的代码，并给我结果：

MySQL返回的查询结果为空（即零行）。

SET @sql = NULL; 
SELECT 
    GROUP_CONCAT(DISTINCT 
    CONCAT(
     'count(case when course = ''', 
     course, 
     ''' then 1 end) AS ', 
     replace(course, ' ', '') 
    ) 
) INTO @sql 
from tbl_course; 

SET @sql = CONCAT('SELECT course, ', @sql, ' from tbl_course 

group by course'); 

PREPARE stmt FROM @sql; 
EXECUTE stmt; 
DEALLOCATE PREPARE stmt; 

Answer 1

查询

set @query = null; 
select 
    group_concat(distinct 
    concat(
     'max(case when `courseid` = ', 
     `courseid`, ' then `course` end) as `course', `courseid`, '`' 
    ) 
) into @query 
from `tbl_course`; 

set @query = concat('select ', @query, ' from `tbl_course` '); 

prepare stmt from @query; 
execute stmt; 
deallocate prepare stmt; 

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