SQL语句过滤结果

Question

我需要过滤的SQL查询结果，根据3个条件：
1.位置
2.医生姓名
3.专业名称

下面是SQL查询，如果所有的3个条件不是空的：

if (location != "" && doctor!="" && specialty!="") 

select Location, ... 
from clinicdoctors 
where Location = @Location and DoctorName = @DoctorName and SpecialtyName = @SpecialtyName 

} 

如果只有位置是空的，

if (location == "" && doctor!="" && specialty!="") 
select Location, ... 
from clinicdoctors 
where Location is not null and DoctorName = @DoctorName and SpecialtyName = @SpecialtyName 

... 

如果我想检查所有的条件，我需要写八个if语句。 在这种情况下我应该怎么做来简化代码？

Answer 1

我认为在代码中执行此操作比使用sql做得更好。没有真正周围没有任何办法，因为查询是如此不同，但简洁的方式做到这一点是：

$loc_where = empty($loc) ? 'Location IS NOT NULL' : "Location = $loc"; 
$doc_where = empty($doc) ? 'AND DoctorName IS NOT NULL' : "AND DoctorName = $doc"; 
$spec_where = empty($spec) ? 'AND SpecialtyName IS NOT NULL' : "AND SpecialtyName = $spec"; 

query ... WHERE $loc_where $doc_where $spec_where 

Answer 2

select Location, ... 
from clinicdoctors 
where 
ISNULL(@Location,Location) = Location 
and ISNULL(@DoctorName,DoctorName) = DoctorName 
and ISNULL(@SpecialtyName,SpecialtyName) = SpecialtyName