How to retrieve all data from table if column value providing null value? How to write a query:

If country = '    ' I need to display all data in table.
If country='algeria', it will display the particular data.
I need both queries in a single query.

I am getting result, but without providing variable how to write query...

declare @country1 varchar(30)
set @country1 = 'asd'

SELECT country_id, country
FROM   country
WHERE  
(
    (@country1  = '') 
    OR 
    (@country1 != '' AND country.country= @country1)
); 




with out  taking any  extra variable i need to  write query.
there@country1
This should do the job.

DECLARE @country1 varchar(30)
SET @country1 = 'asd'

SELECT country_id, country
FROM   country
WHERE country.country LIKE IF(@country = '', '%', @country); 


The IF statement works like this : IF(condition, ifverifiedcondition, else);