使用 PHP 循环或 MySQL 重构坏数据库

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问题描述

我有一个 PHP 项目的特例，我正在使用一个没有第三范式结构的数据库.该数据库仅包含 1 个带有大量列的表.一些应该在单独表中的数据被夹在 1 列中，用某个符号(在本例中为分号;")分隔.

I have a special case with a PHP project where I am working with a database without a 3rd normal form structure. The database consists of only 1 table with loads of columns. Some data that is supposed to be in a separate table, is clamped in 1 column, separated by a certain sign (in this case, semicolon ";").

还有其他列，应将钳位数据移动到上述相同的分隔表中.这一定很令人困惑，所以让我详细说明一下:

There is also other columns where clamped data should be moved to the same separated table as mentioned. This must be confusing, so let me elaborate:

**HugeTable**
id |  Column1      |  Column2     |  Column3

123 |Data1;Data2 Data3;Data4 Data5;Data6

123 | Data1;Data2 Data3;Data4 Data5;Data6

我需要将上面的数据放在一个单独的表中，如下所示:

I need to put the data above in a separate table that looks like this:

**NewTable**
id   |  idHugeTable  |  Column1  |  Column2  |  Column3
 1   |  123          |  Data1    |  Data3    |  Data5
 2   |  123          |  Data2    |  Data4    |  Data6

所以对于大表中的每一个钳位数据，我都需要在新表中新建一行.这个过程将帮助我规范化数据库，使其至少是可行的.现在简直是噩梦.这需要通过 PHP 或 MySQL 来完成，最好是 PHP，因为循环更容易通过脚本语言进行每次循环的一次性查询.

So for each clamped data in the huge table, I need to make a new row in the new table. This process would help me to normalize the database so that it is at least workable. Right now it's a nightmare. This needs to be done either through PHP or MySQL, preferably PHP since looping is easier for one-shot queries per loop through the scripting language.

我在 PHP 中尝试过的示例代码:

Example code of what I have tried in PHP:

$delimiter = ";";
$query = "SELECT * FROM HugeTable";

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

while ($row = mysqli_fetch_assoc()){
    $column1_data = explode($delimiter, $row['Column1']);
    $column2_data = explode($delimiter, $row['Column2']);
    $column3_data = explode($delimiter, $row['Column3']);

    foreach ($column1_data as $key => $value){
        //skip if empty value
        if ($value == ""){
            continue;
        }
        else{
            $query_ins = "INSERT INTO NewTable (idHugeTable, Column1, Column2, Column3) VALUES (".$row['id'].", ".$column1_data[$key].", ".$column2_data[$key].", ".$column3_data[$key].");";
            mysqli_query($connection_var, $query_ins);
        }//end if
    }//end foreach
}//end while

mysqli_close($connection_var);

推荐答案

不需要 PHP.您只能使用纯 MySQL 代码来完成.

No PHP is needed. You can do it with pure MySQL code only.

创建表格/插入表格

CREATE TABLE HugeTable
    (`Column1` VARCHAR(11), `Column2` VARCHAR(11), `Column3` VARCHAR(11))
;

INSERT INTO HugeTable
    (`Column1`, `Column2`, `Column3`)
VALUES
    ('Data1;Data2', 'Data3;Data4', 'Data5;Data6')
; 

CREATE TABLE NewTable
   (`Column1` VARCHAR(11), `Column2` VARCHAR(11), `Column3` VARCHAR(11))
;

首先我们需要 MySQL 来生成数字.此 MySQL 代码生成 1 到 100.所以最终的查询将支持多达 100 个分隔值.

First we need MySQL to generate numbers. This MySQL code generates 1 to 100.So the final query will support up to 100 separated values.

查询

SELECT 
 @row := @row + 1 AS ROW
FROM (
  SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
) row1
CROSS JOIN (
  SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
) row2
CROSS JOIN (
  SELECT @row := 0 
) init_user_params

结果

现在我们可以看看一个方法来分离;分隔符.我们可以为此使用嵌套的 SUBSTRING_INDEX 函数

Now we can look at a method to separate on the ; delimiter. We can use nested SUBSTRING_INDEX functions for that

查询

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX('Data1;Data2', ';', 1), ';', -1) AS DATA

结果

data    
--------
Data1

如果我们想要我们可以使用的第二个单词，您只能看到返回第一个单词

You can see only the first word is returned if we want the second word we can use

查询

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX('Data1;Data2', ';', 2), ';', -1) AS DATA

结果

data    
--------
Data2

现在我们结合数字生成器和SUBSTRING_INDEX来生成数据

Now we combine the number generator and the SUBSTRING_INDEX to generate the data

查询

SELECT 
  DISTINCT
   SUBSTRING_INDEX(SUBSTRING_INDEX(Column1, ';', rows.row), ';', -1) Column1
 , SUBSTRING_INDEX(SUBSTRING_INDEX(Column2, ';', rows.row), ';', -1) Column2
 , SUBSTRING_INDEX(SUBSTRING_INDEX(Column3, ';', rows.row), ';', -1) Column3
FROM (
  SELECT 
   @row := @row + 1 AS ROW
  FROM (
    SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
  ) row1
  CROSS JOIN (
    SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
  ) row2  
  CROSS JOIN (
    SELECT @row := 0 
  ) init_user_params
)
 ROWS
CROSS JOIN 
 HugeTable

结果

Column1  Column2  Column3  
-------  -------  ---------
Data1    Data3    Data5    
Data2    Data4    Data6

查询新表

INSERT INTO 
  NewTable
SELECT 
  DISTINCT
   SUBSTRING_INDEX(SUBSTRING_INDEX(Column1, ';', rows.row), ';', -1) Column1
 , SUBSTRING_INDEX(SUBSTRING_INDEX(Column2, ';', rows.row), ';', -1) Column2
 , SUBSTRING_INDEX(SUBSTRING_INDEX(Column3, ';', rows.row), ';', -1) Column3
FROM (
  SELECT 
   @row := @row + 1 AS ROW
  FROM (
    SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
  ) row1
  CROSS JOIN (
    SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
  ) row2  
  CROSS JOIN (
    SELECT @row := 0 
  ) init_user_params
)
 ROWS
CROSS JOIN 
 HugeTable

查询

SELECT * FROM NewTable

结果

Column1  Column2  Column3  
-------  -------  ---------
Data1    Data3    Data5    
Data2    Data4    Data6

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