Question

我正在尝试创建我认为是一个调用列名参数的相当简单的过程。

这是我创建的程序：

    CREATE DEFINER=`root`@`%` PROCEDURE `test`(in col varchar(225))
BEGIN
-- Column of Averages
DROP temporary TABLE IF EXISTS temp; 

CREATE temporary TABLE IF NOT EXISTS temp AS 
  SELECT col, 
         Round(Avg(bcount), 0) AS `Average # of Loans` 
  FROM   (SELECT col, 
                 Count(borrower) AS bcount 
          FROM   whatif_dataset 
          WHERE  loan_lienposition = 'first' 
          GROUP  BY col, 
                    Month(Str_to_date(status_fundingdate, '%m/%d/%Y')), 
                    Year(Str_to_date(status_fundingdate, '%m/%d/%Y')))AS dt 
  GROUP  BY col; 

END

然而，当我打电话给程序时，我只得到一条记录，即：

Col                Average # of Loans
'Passed Parameter'   757

在我看来，参数没有正确传递。 MYSQL中有一些限制，不允许我这样做吗？

当我使用特定列名称currentprocessor运行相同的查询时，这是所需的结果：

    currentprocessor    Average # of Loans
    proc1               20
    proc2               12
    proc3               8
    proc4               22
    proc5               24

Answer 1

我能够通过使用准备好的声明来纠正这个问题

 CREATE DEFINER=`root`@`%` PROCEDURE `test`(in col varchar(225))
BEGIN
-- Column of Averages
DROP temporary TABLE IF EXISTS temp; 


SET @sql= CONCAT('SELECT ', col,',', 
         'Round(Avg(bcount), 0) AS `Average # of Loans` 
  FROM   (SELECT ', col,', 
                 Count(borrower) AS bcount 
          FROM  whatif_dataset 
          WHERE  loan_lienposition = ''first'' 
          GROUP  BY ', col,', 
                    Month(Str_to_date(status_fundingdate, "%m/%d/%Y")), 
                    Year(Str_to_date(status_fundingdate, "%m/%d/%Y")))AS dt 
  GROUP  BY ', col); 

  PREPARE stmt FROM @sql;
  EXECUTE stmt;
  DEALLOCATE PREPARE stmt;

END

无法使用子查询传递Mysql过程中的参数

1 个答案: