使用AND运算符的Mysql搜索查询：过滤掉空参数

I have a search query build with OR, but I'd like to use the same with AND to get less results. Unfortunatly, as some parameters (VatStatut, VarDomaine, etc.) are left empty in the input form, I get no results at all. How can I filter out these null parameters?I have a search query build with OR, but I'd li