使用 MySQL，我如何遍历更新触发器中的字段以比较更改日志的新旧值？

Question

当日志记录打开时，我正在尝试使用 MySQL 中的触发器来更新带有表更改的日志表。

UPDATE 触发器需要遍历表的所有字段，比较数据变化（OLD.fieldname NEW.fieldname），然后将字段名称和数据写入日志表。

我编写的代码必须明确命名每个字段。有些表有很多字段，我不想手动输入所有字段名称。

有没有办法以编程方式遍历表的字段，以便我可以创建一个存储过程来调用？

我的代码：

CREATE DEFINER=`root`@`localhost` TRIGGER `trgUserUpd` AFTER UPDATE ON `user`
FOR EACH ROW BEGIN
DECLARE rChanges TEXT DEFAULT '';

IF BINARY(OLD.userName) <> BINARY(NEW.userName) THEN
  SET rChanges := CONCAT('userName: ', OLD.userName, ' => ', NEW.userName);
END IF;

IF BINARY(OLD.fullName) <> BINARY(NEW.fullName) THEN
  IF rChanges <> '' THEN
    SET rChanges := CONCAT(rChanges, '
');
  END IF;
  SET rChanges := CONCAT(rChanges, 'fullName: ', OLD.fullName, ' => ', NEW.fullName);
END IF;

IF BINARY(OLD.initials) <> BINARY(NEW.initials) THEN
  IF rChanges <> '' THEN
    SET rChanges := CONCAT(rChanges, '
');
  END IF;
  SET rChanges := CONCAT(rChanges, 'initials: ', OLD.initials, ' => ', NEW.initials);
END IF;

IF BINARY(OLD.password) <> BINARY(NEW.password) THEN
  IF rChanges <> '' THEN
    SET rChanges := CONCAT(rChanges, '
');
  END IF;
  SET rChanges := CONCAT(rChanges, 'password changed');
END IF;

IF BINARY(OLD.salt) <> BINARY(NEW.salt) THEN
  IF rChanges <> '' THEN
    SET rChanges := CONCAT(rChanges, '
');
  END IF;
  SET rChanges := CONCAT(rChanges, 'salt: ', OLD.salt, ' => ', NEW.salt);
END IF;

IF BINARY(OLD.administrator) <> BINARY(NEW.administrator) THEN
  IF rChanges <> '' THEN
    SET rChanges := CONCAT(rChanges, '
');
  END IF;
  SET rChanges := CONCAT(rChanges, 'administrator: ', OLD.administrator, ' => ', NEW.administrator);
END IF;

IF BINARY(OLD.active) <> BINARY(NEW.active) THEN
  IF rChanges <> '' THEN
    SET rChanges := CONCAT(rChanges, '
');
  END IF;
  SET rChanges := CONCAT(rChanges, 'active: ', OLD.active, ' => ', NEW.active);
END IF;

CALL ChangeNotify('user', OLD.id, rChanges, 'update');
END;

似乎准备好的语句也不起作用。我刚试过：

BEGIN
DECLARE rChanges TEXT DEFAULT '';
DECLARE eof INT DEFAULT FALSE;
DECLARE field CHAR(50) DEFAULT '';
DECLARE query, stmt CHAR(200) DEFAULT '';
DECLARE oldValue, newValue TEXT DEFAULT '';

DECLARE fields CURSOR FOR
SELECT column_name
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'user'
ORDER BY ordinal_position;

DECLARE CONTINUE HANDLER FOR NOT FOUND SET eof = TRUE;

OPEN fields;

REPEAT
  FETCH fields INTO field;
  IF NOT eof THEN
    SET query = CONCAT('SELECT OLD.', field, ', NEW.', field, ' INTO oldValue, newValue');
    PREPARE stmt FROM query;
    EXECUTE stmt;
    IF BINARY(oldValue) <> BINARY(newValue) THEN
      IF rChanges <> '' THEN
        SET rChanges := CONCAT(rChanges, '
');
      END IF;
      SET rChanges := CONCAT(rChanges, field, ': ', oldValue, ' => ', newValue);
    END IF;
  END IF;
UNTIL eof = TRUE;
END REPEAT;

CLOSE fields;

CALL ChangeNotify('user', OLD.id, rChanges, 'update');
END

这甚至不会保存（除非我有什么问题）。

Answer 1

使用 DB 和 Table 试试下面的代码，它可能会有所帮助。让我知道它是否对您有帮助。

调用 ATESTE('tablename','dbname')

 CREATE PROCEDURE `ATESTE`(tablename varchar(100),schemaname varchar(100))
    BEGIN
    DECLARE rChanges MEDIUMTEXT;
    DECLARE field VARCHAR(50);
    DECLARE cmdquery MEDIUMTEXT;
    DECLARE oldValue, newValue VARCHAR(50);
    DECLARE myfields MEDIUMTEXT;
    DECLARE mPos integer;        

    set myfields = (SELECT group_concat(column_name)
    FROM INFORMATION_SCHEMA.COLUMNS
    WHERE table_name = tablename and table_schema= schemaname
    ORDER BY ordinal_position);

      set rChanges = '';
      set mPos = Position("," in myfields);

    myloop: While(mPos > 0) Do

        set field = trim(substring(myfields,1,mPos-1));    
        set myfields = trim(substring(myfields,mPos+1)); 
        set mPos = Position("," in myfields);    
        set oldValue =  CONCAT('old.',field);
        set NewValue =  CONCAT('new.',field);   


        IF rChanges <> '' THEN
           SET rChanges = CONCAT(rChanges, '\r\n');
         END IF;

        SET rChanges = CONCAT(rChanges, field, ' : ', oldValue, ' => ', newValue);    

      End While;  

     -- select rChanges;  

     CALL ChangeNotify('user', OLD.id, rChanges, 'update');

    END