Using concat() in INTO OUTFILE gives me error code 1064

Question

I'm trying to execute a query and export its results to a csv file with a formatted current_timestamp in its file name.

• The query itself (excluding from INTO OUTFILE and onwards) executes just fine.
• If I pass a simple string to INTO OUTFILE it exports to csv just fine i.e. making INTO OUTFILE 'C:\path\to\file.csv'.
• If I execute the SELECT CONCAT(..) function and its parameters in another query window, I get a positive looking string returned so I know the concat function is fine, it produces C:\ProgramData\MySQL\MySQL Server 5.6\Uploads\2020-10-20_043918.csv.

I feel like INTO OUTFILE annoyingly doesn't expect anything other than a simple string, hopefully I'm wrong though. Does anyone have any insight to this?

SELECT
    COUNT(*) AS AgentCount,
    clients.ClientId,
    clients.Name AS ClientName,
    computers.RouterAddress
FROM
    computers
LEFT JOIN 
    clients
ON
    computers.ClientId = clients.ClientId
GROUP BY
    computers.RouterAddress
ORDER BY
    AgentCount DESC 
INTO OUTFILE 
    CONCAT('C:\\ProgramData\\MySQL\\MySQL Server 5.6\\Uploads\\', DATE_FORMAT(CURRENT_TIMESTAMP, '%Y-%m-%d_%H%i%s'), '.csv')
FIELDS TERMINATED BY 
    ','
ENCLOSED BY 
    '"'
LINES TERMINATED BY 
    '\r\n'

Answer 1

select ... into outfile does not support variables, as you are finding out. What you ask for requires dynamic SQL:

SET @sql = CONCAT_WS('\r\n',
    'SELECT',
    '   COUNT(*) AS AgentCount,',
    '   clients.ClientId,',
    '   clients.Name AS ClientName,',
    '   computers.RouterAddress',
    'FROM',
    '   computers',
    'LEFT JOIN',
    '   clients',
    'ON',
    '   computers.ClientId = clients.ClientId',
    'GROUP BY',
    '   computers.RouterAddress',
    'ORDER BY',
    '   AgentCount DESC',
    CONCAT('INTO OUTFILE \'', TRIM(BOTH '\'' FROM QUOTE(@@secure_file_priv)), DATE_FORMAT(CURRENT_TIMESTAMP, '%Y-%m-%d_%H%i%s'), '.csv\''),
    'FIELDS TERMINATED BY \',\'',
    'ENCLOSED BY \'\"\'',
    'LINES TERMINATED BY \'\\r\\n\'');

    PREPARE statement FROM @sql;

    EXECUTE statement;
    DEALLOCATE PREPARE statement;