MySQL 游标获取空值

Question

从游标中提取的数据为 NULL。但是我的查询 select id from Projects 返回的行数是正确的。我在我的程序循环中放了一个 select 语句来调试。它为 id 返回 null。我已经关注了这个 [https://dev.mysql.com/doc/refman/5.5/en/cursors.html] 这段代码有什么问题？

DELIMITER $$

CREATE DEFINER=`root`@`localhost` PROCEDURE `ReportDiffProDiffFinYear`()
BEGIN

DECLARE id INT;
DECLARE sqlstr varchar(10000) default "select financialYear as 'name' "; 
DECLARE done INT DEFAULT FALSE;
DECLARE cur1 CURSOR FOR select id from Projects; /* My CURSOR QUERY*/
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;


 OPEN cur1;

 read_loop: LOOP
  FETCH cur1 INTO id;
  select id;
  IF done THEN
  LEAVE read_loop;
  END IF;
  set sqlstr = concat(sqlstr, ", sum(if(projects_id=",id,",0,1)) ");
  END LOOP;

  CLOSE cur1;
   set @sqlstr = concat(sqlstr," from (select * from WaterPoints  where status='Waterpoint Complete') as wp, (select id,financialYear from ProjectDetails) as pd where pd.id=wp.projectDetails_id group by  pd.financialYear");

 prepare stmt from @sqlstr;
 execute stmt;
 deallocate prepare stmt;
 END

Answer 1

我认为您的变量名 id 与游标查询冲突，因此游标查询获取 id 变量的值（null），而不是 id 的值projects table。更改变量名称或使用 projects.id 引用查询中的列。

MySQL 游标获取空值

MySQL Cursors fetching null value

mysql

stored-procedures

cursor