$math = '%s*%s';
    $str  = sprintf($math, 5, 6);
    $result=eval("return $str;");
    var_dump($result);

Give each product a flag directly, and then save the company in turn. When matching, you only need to match the flag to find the formula.

Constructor, determines the execution content based on the parameters passed in

select 商品A "商品名", 数量X时长X单价 "总计"
from table
where 商品=商品A
union all
select 商品B "商品名", 数量X单价 "总计"
from table
where 商品=商品B

If it is product A

select 商品B "商品名", 数量X单价 "总计"
from table
where 商品=商品B

No result will be returned