这个问题是关于mysql的。我正在从一个.csv文件中读取如下所示的数据
原始表格

------------------------------------
Id      2018M01   2018M02  2018M03
------------------------------------
EMEA     3        1          4
ASPAC    4        5          4
ASPAC    1        2          1

预期结果

---------------------
ID        Month     Qty
---------------------
EMEA      2018M01    3
EMEA      2018M02    1
EMEA      2018M03    4
ASPAC     2018M01    4
.......

“月份”列标题是动态的，即每个月都会有新月份，旧月份将被删除。但是，列的总数将保持不变。
因此，每当month列标题更改时，我都希望sql代码能够动态读取并提供正确的结果，而无需手动更改代码的几个部分。
我写了以下代码；代码是取消月份列的IVOT。不过，我测试了代码，手动更改了.csv文件头，将2018m03更改为2018m04，然后重新运行sql代码，但它似乎仍然打印旧数据。我做错什么了？
谢谢您。我对sql相当陌生。

DROP TABLE IF EXISTS book;

CREATE TABLE book (
    ID VARCHARACTER(10),
    2018M01 decimal(4,2),
    2018M02 decimal(4,2),
    2018M03 decimal(4,2)
);

LOAD DATA LOCAL INFILE '/Users/blytonpereira/Desktop/Book1.csv' REPLACE INTO TABLE book 
FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n' IGNORE 1 LINES;

DESCRIBE book;

SELECT ID, '2018M01' AS month, 2018M01 AS qty from book
UNION ALL
SELECT ID, '2018M02' AS month, 2018M02 AS qty from book
UNION ALL 
SELECT ID, '2018M03' AS month, 2018M03 AS qty from book;

SET @sql = NULL;

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

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

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