超过3000列的mySql动态数据透视查询 [英] mySql Dynamic Pivot Query with over 3000 columns

问题描述

早安， 我正在使用动态数据透视查询按月生成产品销售的交叉表.超过3K的产品，因此意味着超过3k的列.当我运行查询时，我得到一个错误.如果我将原始表中的行数限制为1586以下，则可以正常运行，输出为16 col，包括"date"字段.我无法解决这个问题，需要一些帮助！请查看下面的代码和错误:

Good Day, I'm using a dynamic pivot query to generate a cross tab of product sales by month. There are just over 3K products so that means over 3k columns. When I run the query I get an error. If I limit the number of rows in the original table to under 1586 it runs fine with an output of 16 col, including the 'date' field. I can't figure this out and need some help! Please see the code and error below:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'max(case when PSHDSTK = ''',
      PSHDSTK,
      ''' then MthSales end) AS `',
      PSHDSTK,
      '`'
    )
  ) INTO @sql
FROM  salesbyrow;

SET @sql = CONCAT('SELECT thedate, ', @sql, ' 
                  FROM salesbyrow
                                    GROUP BY thedate');

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

我得到的错误是

[Err] 1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM salesbyrow
                                    GROUP BY thedate' at line 2

推荐答案

在一个小样本上，一切似乎对我来说都很好. 您确定在PSHDSTK列中没有引号或某些东西可能破坏您的@sql字符串吗?

Everything seems to be working just fine for me on a small sample. Are you sure there are no quotes or something that may break your @sql string in the PSHDSTK column?

添加SELECT @sql用于调试目的，然后执行语句(如下所示).

Add SELECT @sql for debugging purposes before execution of your statement (shown below).

此外，请注意字符串变量和GROUP_CONCAT的MySQL最大大小.但这在执行查询之前查看时应该很清楚.

Also, beware of MySQL max size for a string variable and GROUP_CONCAT. But that should become clear when you view your query before executing it.

如果GROUP_CONCAT的最大长度为限制(默认为1024)，则应更改其长度的临时设置(会话范围).通过以下方式完成:

If GROUP_CONCAT max length is the limit (1024 by default) you should alter the temporary setting (session-scope) for length of it. It's done by:

SET SESSION group_concat_max_len = 10000 -- to set it to 10 000

---

示例:

---

Sample:

create table salesbyrow(thedate int, PSHDSTK varchar(2), MthSales int);
insert into salesbyrow(thedate,PSHDSTK,MthSales) 
  values (1, 'a1', 6),(1, 'a2', 5), (1, 'a1', 3);

您的代码:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'max(case when PSHDSTK = ''',
      PSHDSTK,
      ''' then MthSales end) AS `',
      PSHDSTK,
      '`'
    )
  ) INTO @sql
FROM  salesbyrow;

SET @sql = CONCAT('SELECT thedate, ', @sql, ' FROM salesbyrow GROUP BY thedate');

健全性检查@sql变量:

select @sql;

声明看起来像这样(正确):

Statement looks like this (correct):

SELECT thedate, max(case when PSHDSTK = 'a1' then MthSales end) AS `a1`,max(case when PSHDSTK = 'a2' then MthSales end) AS `a2` FROM salesbyrow GROUP BY thedate

现在执行中...

prepare stmt from @sql;
execute stmt;

结果:

thedate     a1  a2
1           6   5

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