Skipping WHERE statement if the variable for that statement is null

Question

I will have a table

TABLE1
ID  Name   Country
1   Anna   Singapore
2   Brad   UK
3   Cassie US

declare @place varchar(20);
set @place=\'US\';

select * from Tab         


        

Answer 1

like and = are equivalent in your situation because you are dealing with text (char, nchar, varchar, nvarchar) values.

Instead of

WHERE  country = @place  

try

WHERE  country like @place  

For the variable set try Instead of

set @place='US'

Try

set @country = isnull('''US''','''%''')

To test this:

declare @country nvarchar(50)
set @country = isnull('''US''','''%''')
print @Country
set @country = isnull(NULL,'''%''')
print @Country

The extra quotes are necessary because in your example you are using explicit values - ' is an escape character and you need a single quote around each value to signify it is NOT a table column. If you were using the COLUMN_NAME you would simply use a single quote around the % character.

Depending on your SQL version you may have to use a different wildcard character. This is fairly a fairly direct and linear solution, although there are risks associated with open variables.