Replace the following if conditions in sqlite

I am trying to replace the following sql query in sqlite but seems like I don't have much options available to write this query completely in sqlite. I am aware of using the where not exists of sqlite but not sure how to use the same when there are nested if conditions after if not exists condition like below. I can take care of this issue in code behind but wanted to know if this can be taken care off completely in a sqlite query.

   IF NOT EXISTS (SELECT col1 from tb1 where tbl.id= @someId)
    BEGIN
    SET NOCOUNT ON;

        IF @someparam=@otherparam
                SELECT col1,col2 from tb1
                where tb1.somecolumn='xyz' or tb1.someothercolumn='pqr' 
                order by col1 

        IF @someparam=@otherparam2 OR @someparam = 'xyz'
                SELECT col1,col2 from tb1
                where tb1.somecolumn='xyz' or tb1.someothercolumn='pqr' 
                order by col1 
    END
ELSE
    BEGIN
        SET NOCOUNT ON;
        IF @someparam2=@otherparam3
                SELECT col1,col2 from tb1
                where tb1.somecolumn='xyz' or tb1.someothercolumn='pqr' 
                order by col1 

        IF @someparam2=@otherparam4 OR @someparam = 'xyz'
            SELECT col1,col2 from tb1
                where tb1.somecolumn='xyz' or tb1.someothercolumn='pqr'
                order by col1  
            END
            END