Mysql 将动态列转换为行

我想知道如何将

表1

解压到

预期结果表

：

Table1
-----------------------------------------
Id       abc  brt ccc ddq eee fff gga hxx
-----------------------------------------
12345     0    1   0   5   0   2   0   0  
21321     0    0   0   0   0   0   0   0   
33333     2    0   0   0   0   0   0   0   
41414     0    0   0   0   5   0   0   1   
55001     0    0   0   0   0   0   0   2   
60000     0    0   0   0   0   0   0   0 
77777     9    0   3   0   0   0   0   0

---

因此，如何将

表1

中的列转置为

预期结果表

，只考虑值>0？

基本上是将数据从列中解压到行中，可以使用UNION ALL。过滤器可以应用于整个未激活的子查询，也可以单独应用于零件

select id, Word, Qty from
(
  select id, 'abc' Word, abc Qty from table1 
  union all
  select id, 'brt', brt from table1
  union all
  select id, 'ccc', ccc from table1
  union all
  select id, 'ddq', ddq from table1
  union all
  select id, 'eee', eee from table1
  union all
  select id, 'fff', fff from table1
  union all
  select id, 'gga', gga from table1
  union all
  select id, 'hxx', hxx from table1
) x
where Qty > 0
order by id;

---

MySQL没有UNPIVOT函数，但您可以使用

UNION-ALL

将列转换为行

基本语法是：

select id, word, qty
from
(
  select id, 'abc' word, abc qty
  from yt
  where abc > 0
  union all
  select id, 'brt', brt
  from yt
  where brt > 0
) d
order by id;

在您的案例中，您声明需要动态列的解决方案。如果是这种情况，则需要使用准备好的语句来生成动态SQL：

SET @sql = NULL;

SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'select id, ''',
      c.column_name,
      ''' as word, ',
      c.column_name,
      ' as qty 
      from yt 
      where ',
      c.column_name,
      ' > 0'
    ) SEPARATOR ' UNION ALL '
  ) INTO @sql
FROM information_schema.columns c
where c.table_name = 'yt'
  and c.column_name not in ('id')
order by c.ordinal_position;

SET @sql 
  = CONCAT('select id, word, qty
           from
           (', @sql, ') x  order by id');


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

---

见

谢谢，Richard。我的表有动态列和未知列。

SET @sql = NULL;

SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'select id, ''',
      c.column_name,
      ''' as word, ',
      c.column_name,
      ' as qty 
      from yt 
      where ',
      c.column_name,
      ' > 0'
    ) SEPARATOR ' UNION ALL '
  ) INTO @sql
FROM information_schema.columns c
where c.table_name = 'yt'
  and c.column_name not in ('id')
order by c.ordinal_position;

SET @sql 
  = CONCAT('select id, word, qty
           from
           (', @sql, ') x  order by id');


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