根据SQL Server WHERE子句中的某些条件引入筛选器

Question

I am forming a dynamic SQL using the following T-SQL

Declare @sql nvarchar(max);
Declare @var1 int = 10, @var2 int = 10, @var3 int = 10

set @sql = 'select col1, col2, col3 
            from table
            where col1 = ' + @var1

IF (@var2 > 0)
BEGIN
    SET @sql += ' AND col2 = ' + CONVERT(NVARCHAR(10), @var2)
END

IF (@var3 > 0)
BEGIN
    SET @sql += ' AND col3 = ' + CONVERT(NVARCHAR(10), @var3)
END

It works fine but I want to convert this as static SQL using case when.

Kindly give some suggestion to convert this statement.

Answer 1

this is the query

select col1,col2,col3 
from table
where col1=@var1 AND
(@var2<=0 OR col2=CONVERT(NVARCHAR(10), @var2)) AND
(@var3<=0 OR col3=CONVERT(NVARCHAR(10), @var3))

Answer 2

Mattia's answer is correct, If you want to use CASE WHEN, then here is an alternative (although I prefer Mattia's)

SELECT
    Col1, Col2, Col3
FROM
    Table1
WHERE
    Col1 = @Var1
AND Col2 = CASE
                WHEN @Var2 > 0 THEN CONVERT(NVARCHAR(10), @var2)
                ELSE Col2
            END
AND Col3 = CASE 
                WHEN @Var3 > 0 THEN CONVERT(NVARCHAR(10), @var3)
                ELSE Col3
            END