mysql + pymysql. Delete data before insert question

  Kiến thức lập trình

First of all, I come from China. So please forget my poor and wrong English!

What I want:

I use mysql to store my data. The data will change everday untill a month pass. So evey day I need to delete old data from mysql and insert new data into tables.

I try use the follow trigger to help me easy my work, but it gets error. Why, what`s wrong!

delimiter $$
drop trigger if exists `insert_sell_before`;
create trigger if not exists `insert_sell_before` before insert on `my_table_name` for each row
declare start_date date;
declare end_date date;
select min(NEW.`date_field`),max(NEW.`date_field`) into start_date,end_date;
delete from `my_table_name` where `date_filed` between start_date and end_date;
(1442, "Can't update table '电话网络情况明细表' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.")

Please help me. Thanks very much!

What` wrong. I can I correct it?

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