Question

这是我的选择声明。它做了什么？

检查数据库中是否已有指定日期的约会
检查用户是否在该特定时间工作。

使用mysql_num_rows($result)我检查是否有任何行。如果它返回0，则可以添加约会，如果它返回其他内容（数据库中已经有约会），则会被阻止。

该声明适用于第1点。如果已经有约会，则返回1或更多。但是当所选日期超出用户的工作小时范围时，它也会返回0.

问题：当用户在特定时间

时，我可以添加哪些内容以获取返回的行（mysql_num_rows返回1或更多）？ >

工作小时范围示例：08:00:00 to 17:00:00。

select * 
from ios_appointments a join ios_workinghours h using(workerid_fk) 
where workerid_fk = 1 
AND h.start <= '19:57:20' AND h.end >= '20:57:20' 
AND ( 
   a.start BETWEEN '2012-12-24 19:57:20'  AND  '2012-12-24 20:57:20' 
   OR  a.end   BETWEEN '2012-12-24 19:57:20'  AND  '2012-12-24 20:57:20' 
   OR (a.start < '2012-12-24 19:57:20' AND a.end > '2012-12-24 20:57:20') 
)

Answer 1

您可以返回一行空值：

select * 
from ios_appointments a join ios_workinghours h using(workerid_fk) 
where workerid_fk = 1 
AND h.start <= '19:57:20' AND h.end >= '20:57:20' 
AND ( 
   a.start BETWEEN '2012-12-24 19:57:20'  AND  '2012-12-24 20:57:20' 
   OR  a.end   BETWEEN '2012-12-24 19:57:20'  AND  '2012-12-24 20:57:20' 
   OR (a.start < '2012-12-24 19:57:20' AND a.end > '2012-12-24 20:57:20') 
)
union
select null, null, null -- how every many column are in the first part
where not exists (
    select * 
    from ios_appointments a join ios_workinghours h using(workerid_fk) 
    where workerid_fk = 1 
    AND h.start <= '19:57:20' AND h.end >= '20:57:20' 
    AND ( 
       a.start BETWEEN '2012-12-24 19:57:20'  AND  '2012-12-24 20:57:20' 
       OR  a.end   BETWEEN '2012-12-24 19:57:20'  AND  '2012-12-24 20:57:20' 
       OR (a.start < '2012-12-24 19:57:20' AND a.end > '2012-12-24 20:57:20') 
    )
)

如果您的查询什么都没找到，则返回一行空值，如果找到行，则返回现在的行。

您可以返回所需的任何值，而不是空值。

找不到任何内容时，为select语句定义返回参数

1 个答案: