Fetch data from table based on multiple columns from same table

Question

I have a table of course :

I want to fetch data from searching based on columns Country, university, level, interest and substream.

Query which I've tried but not getting better result.

select *
from edu_college_desc
where (country = @country and
       university = @university and
       leveln = @level and
       interest = @interest and
       substream=@substream)
   or (country = @country or
       university = @university or
       leveln = @level or
       interest = @interest or
       substream = @substream) 

What I want to do is: if select only country then the data should come based on only country or if I select only stream then data fetched based from stream only if I select both or more then data fetch should be based on those columns.

How can I get perfect results?

Answer 1

Try this method,

select * from edu_college_desc 
where   country     =   ISNULL(@country ,country)
    and university  =   ISNULL(@university ,university)
    and leveln      =   ISNULL(@level ,leveln)
    and interest    =   ISNULL(@interest ,interest
    and substream   =   ISNULL(@substream,substream)

In this you can pass the value NULL to any of the parameters if it is not selected.(ie If you have set value only for @university and others are NULL , then result will be university = @university )

Answer 2

For each category, check if the parameter is null (not given) or the same as specified:

select *
from edu_college_desc
where (@country is null or country = @country)
  and (@university is null or university = @university)
  and etc...

And, of course, you can also use MS SQL Server's ISNULL , just as in Abdul Rasheed answer. Convenient but less portable.

Answer 3

您的查询应类似于：

SELECT * FROM edu_college_desc WHERE (@country IS NULL OR country = @country) AND (@university IS NULL OR university = @university) AND (@level IS NULL OR level = @level ) AND (@interest IS NULL OR interest = @interest) AND (@substream IS NULL OR substream= @substream)

Answer 4

此代码肯定会为您提供帮助。

SELECT * FROM edu_college_desc WHERE (country = @country or isnull(@country,0)= 0) AND (university = @university or isnull(@university,0)= 0) AND (leveln = @leveln or isnull(@leveln,0)= 0) AND (interest = @interest or isnull(@interest,0)= 0) AND (substream=@substream or isnull(@substream,0)= 0)