如何使用php在mysql的单个记录中的几个字段中选择和显示最大（和最小）值

I have a table which lists several tours and for each tour there are several categories of accommodation types with different prices, along with a lot of other fields such as dates, deadlines etc. It was easy to set things up to display the array showing the tour, dates, deadlines but I also want to select and display the maximum (and minimum when not 0) accommodation rates for each tour. I may not be understanding some of the answers I'm seeing but most seem to be looking for max values within a field rather than across fields. I'm assuming once I know how to find the max value, finding the min value would be the same basic procedure.I have a table which lists several tours and fo