mysql中的列到行交叉表转换

我想在MySQL中创建交叉表

有两个表TABL1和TBL2，我不知道如何将列转换为行

请给我一个解决办法

我的代码如下所示：

从TBL1 t1左键选择*在t1上连接TBL2 t2。des=t2.des

TBL1 :
DES
A
C
D
E

TBL2
ID DES
1  A
2  C
3

RESULT THAT I NEED

ID   A   C  D  E
1    1
2        1
3

关于，

试试这个：

SELECT
    t2.id,
    SUM(IF(t1.des IS NOT NULL AND t1.des = 'A',1,0)) as 'A',
    SUM(IF(t1.des IS NOT NULL AND t1.des = 'C',1,0)) as 'C',
    SUM(IF(t1.des IS NOT NULL AND t1.des = 'D',1,0)) as 'D',
    SUM(IF(t1.des IS NOT NULL AND t1.des = 'E',1,0)) as 'E'
FROM
    TBL2 t2
LEFT JOIN TBL1 t1
    ON t2.des = t1.des
GROUP BY
    t2.id

---

对于某些自动化，您可以尝试使用以下步骤：

制作一个光标来读取TBL1，这样你就知道你有多少个COL了

DECLARE curs CURSOR FOR SELECT des FROM TBL1;

在游标内部，需要为Select语句创建dynamicSQL。像这样的事情：

....
FETCH curs INTO cDes;
....
set @sel = concat(@sel, 
', SUM(IF(t1.des IS NOT NULL AND t1.des = ''', cDes,''',1,0)) as ''',cDes, '''');
...
CLOSE curs;

set @crosstab = concat('select t2.id', @sel, 
                        'FROM TBL2 t2
                        LEFT JOIN TBL1 t1 ON t2.des = t1.des
                        GROUP BY t2.id');

PREPARE STMT FROM @crosstab;
EXECUTE STMT;
DEALLOCATE PREPARE STMT;

完成后，您需要完成dynamicSQL的完整版本。类似这样的：

....
FETCH curs INTO cDes;
....
set @sel = concat(@sel, 
', SUM(IF(t1.des IS NOT NULL AND t1.des = ''', cDes,''',1,0)) as ''',cDes, '''');
...
CLOSE curs;

set @crosstab = concat('select t2.id', @sel, 
                        'FROM TBL2 t2
                        LEFT JOIN TBL1 t1 ON t2.des = t1.des
                        GROUP BY t2.id');

PREPARE STMT FROM @crosstab;
EXECUTE STMT;
DEALLOCATE PREPARE STMT;

---

这可能会有帮助you@JamDara在mysql中，您无法以动态方式透视数据，您必须手动进行此操作。。。或者更好的方法是从脚本生成查询。我同意@Stephan的观点，我们的oracle数据库也有类似的问题。不能将行值动态转换为字段。