在 MySQL 存储例程中创建动态 WHERE 子句

Question

对这个问题的任何帮助都会很好，因为它让我发疯。我的 MYSQL 数据库中的一个表包含货币的详细信息，尽管那里似乎有很多动态 WHERE 子句，但我已经搜索了几十个似乎都没有满足缺少的变量的需求。

TABLE coin (
  coinID smallint(6) NOT NULL AUTO_INCREMENT,
  coinCountry smallint(6) NOT NULL,
  coinDenom smallint(6) NOT NULL,
  coinMinted smallint(6) NOT NULL,
  coinImageLocation varchar(128) NOT NULL,
  coinPgeTitle varchar(45) NOT NULL,
  PRIMARY KEY (coinID)
) 

我想要一个存储例程中的动态“WHERE”子句，它接受三个参数，其中一个参数是强制性的，并且总是有一个值，另外两个是任意的，要么有值，要么没有

我已经编写了这个存储例程，并且在某个地方隐藏了问题

DELIMITER $$


CREATE DEFINER=`root`@`localhost` PROCEDURE `procFilterCoins`
(

/*******************************************************

Proc     :  Filter the coins returned by adjusting the WHERE Clause.

IN   :  iCountry (The CountryID) a mandatory value

IN   :  iDenom (The DenominationID) a discretionary value

IN   :  iMinted (The year minted) a discretionary value

OUT      :  filtered coins recordset

********************************************************/

IN iCountry int(11), 

IN iDenom int(11), 

IN iMinted int(11)
)

BEGIN

/* somewhere to hold our where clause*/

DECLARE strWhere varchar(100);


set strWhere = '((coinCountry = ';

IF iDenom > 0 and iDenom IS NOT NULL THEN

    set strWhere = concat(strWhere, iCountry, ") AND (coinDenom = ", iDenom, ')');

ELSE

    set strWhere = concat(strWhere, iCountry, ')');

END IF;


IF iMinted > 0 and iMinted IS NOT NULL THEN

    set strWhere = concat(strWhere, " AND (coinMinted = ", iMinted, '))');

ELSE

    set strWhere = concat(strWhere, ')');
END IF;


/*Extract the records via prepared view*/
SELECT * FROM vAllcoins WHERE + strwhere;


END

我已经使用MySQL Workbench 5.2.46.CE测试了以下数据

调用 procfiltercoins(18,null,1948); 产生... WHERE ((coinCountry = 18) AND (coinMinted = 1948)); 没有返回记录

调用 procfiltercoins(103,4,1948,@out); 产生...

WHERE ((coinCountry = 103) AND (coinDenom = 4) AND (coinMinted = 1948));

没有返回记录

调用 procfiltercoins(18,2,null,@out); 产生...

WHERE ((coinCountry = 18) AND (coinDenom = 2));

没有返回记录

我已经在 Access 数据库中复制了所有这些，没有任何问题

Answer 1

尝试使用准备好的语句：

SET @query = CONCAT("SELECT * FROM vAllcoins WHERE ",strwhere);

PREPARE stmt FROM @query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

不确定您想对查询结果做什么。把它放在一个视图中？

SET @query = CONCAT("CREATE VIEW myView as SELECT * FROM vAllcoins WHERE ",strwhere);

PREPARE stmt FROM @query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

祝你好运！