选择查询中的逻辑错误

Question

mysql> Create Procedure sp_Getnewtask(IN sdate datetime, IN edate datetime,IN sid   int,IN tid int,OUT outmsg varchar(50))
-> begin
-> if not exists(
-> SELECT * FROM tbltask WHERE (startdate BETWEEN sdate AND edate)OR (enddate BETWEEN sdate AND edate) OR (sdate BETWEEN startdate AND enddate) OR (edate BETWEEN startdate AND enddate) OR Sid=Sid OR Tid=tid ) then
-> set outmsg = 'ADDED SUCESSFULLY';
-> else
-> set outmsg = 'RECORD ALREADY PRESENT';
-> end if;
-> end $$

mysql> select * from tbltask;

| tblid | startdate           | enddate             | Sid  | Lid  |

|     1 | 2011-05-20 00:00:00 | 2011-05-29 00:00:00 | NULL | NULL |

1 row in set (0.00 sec)

即使数据库中没有记录，它也会显示为记录已存在，

如果我从选择查询中删除 sid,tid 它工作正常， 请提出一些想法以便正确运行输出

当我尝试调用该程序时， 它返回为，

 mysql> call sp_Getnewtask('2011-05-20','2011-05-29',6,8,@outmsg);
-> select @outmsg;
-> $$

查询正常，0 行受影响（0.00 秒）

| @outmsg                |

| RECORD ALREADY PRESENT |

集合中的 1 行（0.00 秒）

但我的实际结果应该是“成功添加”

Answer 1

只有在您的选择语句中没有选择任何记录时才应该报告“添加成功”，但如果您在call sp_Getnewtask('2011-05-20','2011-05-29',6,8,@outmsg); 中输入变量，您实际上会在所有 WHERE 的 OR'd 条件中触发您的 6 个条件中的四个。

编辑添加：

我已经运行了以下（包括结果）。我所做的是更改变量的名称，这样您就不会得到始终正确的 WHERE 语句（SID=SID or TID=TID 将始终正确）。我还更改了 SELECT 语句以匹配您作为示例提供的表中的字段名称。

CREATE TABLE tbltask
    (
        tblid int,
        startdate datetime,
        enddate datetime,
        sid int,
        lid int
    );

INSERT INTO `tbltask`(`tblid`, `startdate`, `enddate`) VALUES (1, '2011-05-20 00:00:00','2011-05-29 00:00:00');

DELIMITER //
CREATE Procedure sp_Getnewtask(IN sdate datetime, IN edate datetime,IN inSid int,IN inLid int,OUT outmsg varchar(50))
begin
if not exists
(
    SELECT * FROM tbltask WHERE (startdate BETWEEN sdate AND edate)OR (enddate BETWEEN sdate AND edate) OR (sdate BETWEEN startdate AND enddate) OR (edate BETWEEN startdate AND enddate) OR Sid=inSid OR Lid=inLid
) then
    set outmsg = 'ADDED SUCCESSFULLY';
else
    set outmsg = 'RECORD ALREADY PRESENT';
end if;
end
//

call sp_Getnewtask('2011-05-20','2011-05-29',6,8,@outmsg);
select @outmsg;

RECORD ALREADY PRESENT

call sp_Getnewtask('2010-05-20','2010-05-29',6,8,@outmsg);
select @outmsg;

ADDED SUCCESSFULLY

就目前而言，这似乎正在做它应该做的事情。如果任一日期范围相交，它将找到记录。如果它们不相交但 sid OR lid 匹配，那么它将找到记录。查找记录使其报告“记录已存在”