在存储过程中对"in"子句使用MySQL用户定义的变量 [英] Using MySQL user-defined variable in stored procedure for 'in' clause

问题描述

当将以逗号分隔的ID字符串(作为varchar)发送到MySQL存储过程时，我不能将该字符串用作IN子句的一部分，并返回正确的结果.字符串被截断为十进制，并且仅使用第一个值.

When sending a string of comma separated ids, as a varchar, to a MySQL stored procedure I can not use the string as part of an IN clause with the correct results returned. The string is truncated as a decimal and only the first value is being used.

我认为我可以通过准备然后执行该语句来解决此问题，但这仍然只返回第一个值的匹配项.

I thought I would be able to get around this by preparing and then executing the statement, but this still only returned a match for the first value.

代码示例可能会让事情变得更清楚.我想将以下内容转换为存储过程(使用in子句动态):

Code examples may make things a bit clearer. I want to convert the following into a stored procedure (with the in clause dynamic):

select id, name from cities where id in (1,2,3);

这是使用准备好的语句的存储过程:

This is my stored procedure using a prepared statement:

DROP PROCEDURE IF EXISTS `cities_select_by_ids` $$
CREATE PROCEDURE `cities_select_by_ids`(
    in _cityIds varchar(1000)
)
BEGIN
SET  @cityIds = _cityIds;

PREPARE stmt FROM '
    select
      id,
      name
    from cities
    where id in (?);
';

EXECUTE stmt USING @cityIds;
DEALLOCATE PREPARE stmt;

END $$
DELIMITER ;

调用存储过程时，只会得到城市"1"的匹配项:

Calling the stored procedure I only get a match for the city '1':

call cities_select_by_ids_prepare('1, 2, 3');

这是用于表和数据的创建和插入脚本:

Here is a create and insert script for the table and data:

CREATE TABLE cities (
  id int(10) unsigned NOT NULL auto_increment,
  name varchar(100) NOT NULL,
  PRIMARY KEY  (`id`)
);
insert into cities (name) values ('London'), ('Manchester'), ('Bristol'), ('Birmingham'), ('Brighton');

推荐答案

由于参数化的工作方式，因此不可能.

due to the way parameterization works, this is not possible.

最接近的它可以得到:

where find_in_set(id, ?)

但这不会像不能使用索引那样缩放.

but this will not scale as as can not use an index.

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