Mysql / Mariadb 查询在查询数据时动态将行转换为列答案

【问题标题】：Mysql / Mariadb query to dynamically convert rows to columns while querying the dataMysql / Mariadb 查询在查询数据时动态将行转换为列
【发布时间】：2017-09-16 15:30:22
【问题描述】：

我查看了Mysql query to dynamically convert rows to columns 的答案，但我无法让它发挥作用，因为我需要加入表格以获取所有信息。你能帮我把“问题”作为列名，如此处所示吗？

datestamp           pay        benefits ...    career advancement
---------------------------------------------------------------------   
2/16/2017 11:55     Somewhat   Slightyly       Slightly
2/16/2017 11:55     Agree      Somewhat        Very

数据如下：

id  datestamp        survey_col           value
-----------------------------------------------
1   2/16/2017 11:55 885457X234X1368SQ001    A3
1   2/16/2017 11:55 885457X234X1368SQ002    A4
1   2/16/2017 11:55 885457X234X1368SQ003    A4
1   2/16/2017 11:55 885457X234X1368SQ004    A3
1   2/16/2017 11:55 885457X234X1368SQ005    A2
1   2/16/2017 11:55 885457X234X1368SQ006    A3
1   2/16/2017 11:55 885457X234X1368SQ007    A4
1   2/16/2017 11:55 885457X234X1368SQ008    A3
1   2/16/2017 11:55 885457X234X1368SQ009    A4
1   2/16/2017 11:55 885457X234X1368SQ010    A1

我正在使用此代码：

   SELECT T.id, T.datestamp, SQ.question, 
      IF(type IN ("K", "N", "S", "T", "Y", "*") AND type NOT IN ("F"),
         T.value,
         IF(parent_qid = 0, SA.answer, SA2.answer)
      ) as answer
      FROM survey_questions SQ 
      JOIN survey_lookup SL ON SL.qid = SQ.qid
      JOIN tmp T ON T.survey_col = SL.survey_col
      LEFT JOIN survey_answers SA ON SA.qid = SQ.qid
         AND SA.code = T.value
         AND SA.language = 'en'
      LEFT JOIN survey_answers SA2 on SA2.qid = SQ.parent_qid
         AND SA2.code = T.value
         AND SA2.language = 'en'
      WHERE SQ.language = 'en'
      ;

提供：

id  datestamp       question                            answer
----------------------------------------------------------------
1   2/16/2017 11:55 Pay                                 Somewhat
1   2/16/2017 11:55 Benefits (health plan, leave, etc.) Slightly
1   2/16/2017 11:55 Career Advancement                  Slightly
1   2/16/2017 11:55 Access to Training                  Somewhat
1   2/16/2017 11:55 Leadership Style                    Very
1   2/16/2017 11:55 Manager/Supervisor Style            Somewhat
1   2/16/2017 11:55 Please enter comments               The company's policies...

当所有数据都在一个表中并且我不必使用连接时，此代码有效。

    SET @sql = NULL;
   SET SESSION GROUP_CONCAT_MAX_LEN = 1000000;  -- default is 1024
   SELECT
      GROUP_CONCAT(DISTINCT
         CONCAT(
            'MAX(IF(question = ''', REPLACE(question,"'", "\\'"), ''', answer, NULL)) AS ''', REPLACE(question,"'", "\\'"), ''''
         )
      ) INTO @sql
      FROM tmp; 

      SET @sql = CONCAT('SELECT row_id, submitdate, ', @sql, ' FROM ', survey_report, ' GROUP BY row_id');

      IF DEBUG = 1 THEN
         SELECT @sql;   
      END IF;

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

这是不使用 REPLACE 功能（我想使用）的尝试。

 SELECT 
  GROUP_CONCAT(DISTINCT
  CONCAT(
  'MAX(IF(SQ.question = ', '''SQ.question''',' 
      IF(type IN ("K", "N", "S", "T", "Y", "*") AND type NOT IN ("F"),
        T.value,
        IF(parent_qid = 0, SA.answer, SA2.answer)
      ) as answer, NULL)) as answer', '''SQ.question''')
  ) INTO @sql
  FROM survey_questions SQ 
  JOIN survey_lookup SL ON SL.qid = SQ.qid
  JOIN tmp T ON T.survey_col = SL.survey_col
  LEFT JOIN survey_answers SA ON SA.qid = SQ.qid
     AND SA.code = T.value
     AND SA.language = 'en'
  LEFT JOIN survey_answers SA2 on SA2.qid = SQ.parent_qid
     AND SA2.code = T.value
     AND SA2.language = 'en'
  WHERE SQ.language = 'en';  

  SET @sql = CONCAT('SELECT id, datestamp, ', @sql, ' FROM tmp GROUP BY id');

  SELECT @sql;   

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

【问题讨论】：

您可能已经知道这称为透视表。您已经发现 MySQL 是多么让人头疼。
我同意。我正在使用非常具有挑战性的软件来获取所需的数据。我使用游标来获取非常慢的数据，但我发现联合使它更快。因此，我使用联合来获取数据，以便创建连接。现在，我正在尝试将其转换为可以在绘图软件中使用的格式。我尝试了几件事，这似乎是最好的，因为它在 11 秒内运行，而其他解决方案我花了 4 分钟。
这是 SQL 是解决问题的错误解决方案的其中一种情况。编写 PHP/Java/任何代码来进行格式化。使用 SQL 提供数据。
谢谢詹姆斯。我正在使用 JBoss Dashbuilder，我认为它是用 java 编写的，所以这是一个选项。不幸的是，我不熟悉java。我可以将数据保存到另一个表中，然后对其进行格式化，但我认为写入磁盘很慢。

标签： mysql dynamic pivot-table dynamic-columns

【解决方案1】：

这可行，但我不想创建另一个表。

DROP TEMPORARY TABLE  IF EXISTS `tmp2`;
CREATE TEMPORARY TABLE tmp2
   SELECT T.id, T.datestamp, SQ.question, 
      IF(type IN ("K", "N", "S", "T", "Y", "*") AND type NOT IN ("F"),
         T.value,
         IF(parent_qid = 0, SA.answer, SA2.answer)
      ) as answer
      FROM survey_questions SQ 
      JOIN survey_lookup SL ON SL.qid = SQ.qid
      JOIN tmp T ON T.survey_col = SL.survey_col
      LEFT JOIN survey_answers SA ON SA.qid = SQ.qid
         AND SA.code = T.value
         AND SA.language = 'en'
      LEFT JOIN survey_answers SA2 on SA2.qid = SQ.parent_qid
         AND SA2.code = T.value
         AND SA2.language = 'en'
      WHERE SQ.language = 'en'
      ;

-- 从tmp2中选择*；

         SET @sql = NULL;
   SET SESSION GROUP_CONCAT_MAX_LEN = 1000000;  -- default is 1024
   SELECT
      GROUP_CONCAT(DISTINCT
         CONCAT(
            'MAX(IF(question = ''', REPLACE(question,"'", "\\'"), ''', answer, NULL)) AS ''', REPLACE(question,"'", "\\'"), ''''
         )
      ) INTO @sql
      FROM tmp2;
      SET @sql = CONCAT('SELECT id, datestamp, ', @sql, ' FROM tmp2 GROUP BY id');

      SELECT @sql;   

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

【讨论】：