is that two values are displayed at the front end, one is the total number of places, and the other is the number of remaining names. For example, a task has a total of 50 places, after the user receives, the total number of times after collection shows the remaining quota, how to achieve this. I feel that the database needs two fields to show these two numbers, but how to relate them, and how to judge that they need to be subtracted? Which boss helps me? this problem has perplexed me for a long time. I don"t know how to achieve it. You"d better have the code to help present it. Thank you very much!