Com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException:You has an error in your SQL syntax; Che

I have encountered this error for a two of times.
1 The name of my field coincides with the keyword of the database.

Desc in is the default descending order of the meaning.
2 The second occurrence of the exception is a bug I encountered during the refactoring code phase. But I can't understand it for the time being, although it solves the mistake.
The code for the delete operation is as follows:

 Public void deleteproduct (Long id) {        = "DELETE from  t_product WHERE id=?" ;        JDBCTEMPLATE.TEMPLATEDML (Sql,id); }

Or the following wording: All is correct.

 Public void deleteproduct (Long id) {        = "DELETE from  t_product WHERE id=" +ID;        JDBCTEMPLATE.TEMPLATEDML (SQL);    }

But there is a problem when you query a result:

 Public Product Getproductbyid (Long ID) {        sql= "SELECT * from  t_product  WHERE id=?" ;        List<Product> list = jdbctemplate.templatedql (sql,id);         return list.size () ==1?list.get (0):null;    }

After the change can be again;

 Public Product Getproductbyid (Long ID) {        sql= "SELECT * from  t_product  WHERE id=" +ID;        List<Product> list = jdbctemplate.templatedql (sql);         return list.size () ==1?list.get (0):null;    }

Com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException:You has an error in your SQL syntax; Che