如果你可以
switch to named parameters,你可以将条件更改为检查参数为null,如下所示：
select e.event_id,a.attempt_id,a.preferred,a.duration,a.location
from event e,attempt a
where
(:ul is null OR e.user_label=:ul)
and (:st is null OR e.start_time=:st)
and (:et is null OR e.end_time=:et)
and (:dmin is null OR e.duration_min=:dmin)
and (:dmax is null OR e.duration_max=:dmax)
and e.event_id=a.event_id
如果你不能切换到命名参数,你仍然可以使用相同的技巧,但你需要为每个可选的参数传递两个参数：如果第二个参数设置,则该对的第一个参数为1,如果第二个参数,则为0一个省略：
select e.event_id,a.attempt_id,a.preferred,a.duration,a.location
from event e,attempt a
where
(? = 1 OR e.user_label=?)
and (? = 1 OR e.start_time=?)
and (? = 1 OR e.end_time=?)
and (? = 1 OR e.duration_min=?)
and (? = 1 OR e.duration_max=?)
and e.event_id=a.event_id
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