一个有效的例子：

<?php
$con=mysqli_connect("localhost","user","password","db_name");
// Check connection
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }

// Your array 
$conversionServiceId = [
    'green'=>'column1',
    'yellow'=>'column2',
    'red'=>'column3'
];

$qstring = "
SELECT id," . $conversionServiceId['green'] . "
  INTO OUTFILE 'e:/result.csv'
  FIELDS TERMINATED BY ','
  LINES TERMINATED BY '\\n'
  FROM nodejs;";

 // uncomment next line if you want to see query string in browser
 //echo $qstring;

mysqli_query($con, $qstring);

mysqli_close($con);

?>

你可以填写你的用户和密码，db\u名称，把这个文件放在你的根文件夹中，然后在浏览器中测试它。

你不能这样把php和sql混在一起。您可以先用sql下载文件，然后打开并用php修改它，或者将转换逻辑移到sql查询本身。
显然，第二种解决方案更有效。
如果转换列表较小，则 CASE （或cte）应：

SELECT 
    column,
    CASE 
        WHEN column2 = 'green'  THEN 1
        WHEN column2 = 'yellow' THEN 2
        WHEN column2 = 'red'    THEN 3
    END column2
    column3
INTO 
    OUTFILE '/path/to/file/result.txt'
    FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
    LINES TERMINATED BY '\n'
FROM yourtable 
WHERE columnx = 'çondition';

如果要处理一个大的转换列表，可以考虑将其存储在数据库表中。假设您的转换表被称为 yourconversiontable 并且有列 old 以及 new ，然后：

SELECT 
    t.column,
    c.new
    t.column3
INTO 
    OUTFILE '/path/to/file/result.txt'
    FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
    LINES TERMINATED BY '\n'
FROM yourtable t
INNER JOIN yourconversiontable c ON t.column2 = c.old
WHERE t.columnx = 'çondition';