MySQL函数仅在未使用传递的参数时才起作用？

Question

我有一个问题，我的函数只有在我不使用我传递的参数时才工作。

这是我想要的代码:

DELIMITER $$

CREATE DEFINER=`root`@`%` FUNCTION `getTableColumns`(schemaName varchar(100), tableName varchar(100), omitColumns varchar(200)) RETURNS varchar(5000) CHARSET latin1
BEGIN
  DECLARE done INT DEFAULT 0;
  DECLARE res  VARCHAR(5000) DEFAULT "";

  DECLARE col  VARCHAR(200);
  DECLARE cur1 CURSOR FOR 
    select COLUMN_NAME from information_schema.columns 
    where table_schema = @schemaName AND table_name = @tableName AND FIND_IN_SET(COLUMN_NAME, @omitColumns) = 0 ORDER BY ORDINAL_POSITION;

  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
  OPEN cur1;
  REPEAT
       FETCH cur1 INTO col;
       IF NOT done THEN 
          set res = CONCAT(res,IF(LENGTH(res)>0,",",""),col);
       END IF;
    UNTIL done END REPEAT;
  CLOSE cur1;
  RETURN res;
END

这是当我用文字字符串替换参数时有效的代码:

DELIMITER $$

CREATE DEFINER=`root`@`%` FUNCTION `getTableColumns`(schemaName varchar(100), tableName varchar(100), omitColumns varchar(200)) RETURNS varchar(5000) CHARSET latin1
BEGIN
  DECLARE done INT DEFAULT 0;
  DECLARE res  VARCHAR(5000) DEFAULT "";

  DECLARE col  VARCHAR(200);
  DECLARE cur1 CURSOR FOR 
    select COLUMN_NAME from information_schema.columns 
    where table_schema = 'test' AND table_name = 'employees' ORDER BY ORDINAL_POSITION;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
  OPEN cur1;
  REPEAT
       FETCH cur1 INTO col;
       IF NOT done THEN 
          set res = CONCAT(res,IF(LENGTH(res)>0,",",""),col);
       END IF;
    UNTIL done END REPEAT;
  CLOSE cur1;
  RETURN res;
END

Answer 1

试试这个:

DELIMITER $$

CREATE DEFINER=`root`@`%` FUNCTION `getTableColumns`(_schemaName varchar(100), _tableName varchar(100), _omitColumns varchar(200)) RETURNS varchar(5000) CHARSET latin1
BEGIN
  DECLARE done INT DEFAULT 0;
  DECLARE res  VARCHAR(5000) DEFAULT "";

  DECLARE col  VARCHAR(200);
  DECLARE cur1 CURSOR FOR 
    select COLUMN_NAME from information_schema.columns 
    where table_schema = _schemaName AND table_name = _tableName ORDER BY ORDINAL_POSITION;

  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
  OPEN cur1;
  REPEAT
       FETCH cur1 INTO col;
       IF NOT done THEN 
          set res = CONCAT(res,IF(LENGTH(res)>0,",",""),col);
       END IF;
    UNTIL done END REPEAT;
  CLOSE cur1;
  RETURN res;
END