SQL語句過濾結果

Question

我需要過濾的SQL查詢結果，根據3個條件：
1.位置
2.醫生姓名
3.專業名稱

下面是SQL查詢，如果所有的3個條件不是空的：

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 

... 

如果我想檢查所有的條件，我需要寫八個if語句。 在這種情況下我應該怎麼做來簡化代碼？

Answer 1

我認爲在代碼中執行此操作比使用sql做得更好。沒有真正周圍沒有任何辦法，因爲查詢是如此不同，但簡潔的方式做到這一點是：

$loc_where = empty($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