透视mysql表返回答案

【问题标题】：Pivot mysql table returns透视mysql表返回
【发布时间】：2018-09-20 12:35:03
【问题描述】：

我正在尝试旋转一个这样创建的 mysql 表

'CREATE TABLE `fundreturns` (
`Timestamp` datetime NOT NULL,
`FundName` varchar(255) NOT NULL,
`MonthYear` datetime NOT NULL,
`Returns` decimal(9,7) DEFAULT NULL,
PRIMARY KEY (`FundName`,`MonthYear`),
CONSTRAINT `FundName` FOREIGN KEY (`FundName`) REFERENCES `fundnames` (`fund_name`))

这样结果将是一个看起来像的表格

Date    Company 1   Company 2   ...Company 200  
-------------------------------------------------
09/18        {Returns                    }              
07/18

并非每家公司每个月都有回报，而且是单个百分比数字，不需要在整个月内累加。我一直在寻找使用 mysql 或 php 的解决方案，我遇到过有关动态 sql 语句的答案并尝试使用

SET @@group_concat_max_len = 32000;

SET @sql_dynamic = (
    SELECT
        GROUP_CONCAT( DISTINCT
            CONCAT(
                'IF(fundname = '''
                , fundname
                , ''', returns, NULL) AS '
                , fundname
            )
        )
    FROM fundreturns
);

SET @sql = CONCAT('SELECT monthyear, ', 
              @sql_dynamic, ' 
           FROM fundreturns
           GROUP BY monthyear'
       );

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

这给了我一个错误

Error Code: 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 '(ACL) Alternative Fund,IF(fundname = 'ABCA Reversion', fundreturns, NULL) AS ABC' at line 1

我做错了什么？有没有更好的方法来做到这一点？

【问题讨论】：

我在你的表中看不到 ACL
你提到了 PHP，所以我无法理解你为什么要尝试在 MySQL 中解决这个问题。
我愿意使用任何可行的方法，我也会使用 PHP。 ACL 是表中的公司名称。
所以它缺少引号。但是 PHP 肯定会提供更好的解决方案。
添加逗号后，大部分值都丢失了，每个日期似乎只有一个值。我见过的PHP方法似乎都需要这个查询

标签： mysql pivot-table

【解决方案1】：

考虑以下...

<?php

/*
CREATE TABLE fundreturns (
Timestamp datetime NOT NULL,
FundName varchar(255) NOT NULL,
Returns decimal(9,7) DEFAULT NULL,
PRIMARY KEY (`FundName`,`Timestamp`)
);


INSERT INTO fundreturns VALUES
('2018-01-01','Piggy',10.2),
('2018-01-02','Piggy',15.1),
('2018-01-03','Piggy',7.4),
('2018-01-04','Piggy',3.9),
('2018-01-05','Piggy',1.2),

('2018-01-01','Kermit',10.5),
('2018-01-02','Kermit',9.9),
('2018-01-03','Kermit',10.5),
('2018-01-04','Kermit',11.9),
('2018-01-05','Kermit',12.2);


SELECT Timestamp
     , FundName
     , Returns
  FROM fundreturns
 ORDER
    BY timestamp
     , fundname;

+---------------------+----------+------------+
| Timestamp           | FundName | Returns    |
+---------------------+----------+------------+
| 2018-01-01 00:00:00 | Kermit   | 10.5000000 |
| 2018-01-01 00:00:00 | Piggy    | 10.2000000 |
| 2018-01-02 00:00:00 | Kermit   |  9.9000000 |
| 2018-01-02 00:00:00 | Piggy    | 15.1000000 |
| 2018-01-03 00:00:00 | Kermit   | 10.5000000 |
| 2018-01-03 00:00:00 | Piggy    |  7.4000000 |
| 2018-01-04 00:00:00 | Kermit   | 11.9000000 |
| 2018-01-04 00:00:00 | Piggy    |  3.9000000 |
| 2018-01-05 00:00:00 | Kermit   | 12.2000000 |
| 2018-01-05 00:00:00 | Piggy    |  1.2000000 |
+---------------------+----------+------------+
*/

require('path/to/connection/stateme.nts');

$query = "
SELECT Timestamp
     , FundName
     , Returns
  FROM fundreturns
 ORDER
    BY timestamp
     , fundname;
";

$result = mysqli_query($db,$query);

$array = array();

while($row = mysqli_fetch_assoc($result)){
$array[] = $row;
}

foreach($array as $v){
$new_array[$v['Timestamp']][$v['FundName']] = $v['Returns'];
}


print_r($new_array);
?>

输出：

Array
(
    [2018-01-01 00:00:00] => Array
        (
            [Kermit] => 10.5000000
            [Piggy] => 10.2000000
        )

    [2018-01-02 00:00:00] => Array
        (
            [Kermit] => 9.9000000
            [Piggy] => 15.1000000
        )

    [2018-01-03 00:00:00] => Array
        (
            [Kermit] => 10.5000000
            [Piggy] => 7.4000000
        )

    [2018-01-04 00:00:00] => Array
        (
            [Kermit] => 11.9000000
            [Piggy] => 3.9000000
        )

    [2018-01-05 00:00:00] => Array
        (
            [Kermit] => 12.2000000
            [Piggy] => 1.2000000
        )

)

【讨论】：